Spirit of Prophecy quotes on the Mark of the Beast for those that would like to know how to better prepare...

"The commencement of that time of trouble," here mentioned does not refer to the time when the plagues shall begin to be poured out, but to a short period just before they are poured out, while Christ is in the sanctuary. At that time, while the work of salvation is closing, trouble will be coming on the earth, and the nations will be angry, yet held in check so as not to prevent the work of the third angel. At that time the "latter rain," or refreshing from the presence of the Lord, will come, to give power to the loud voice of the third angel, and prepare the saints to stand in the period when the seven last plagues shall be poured out. {EW 85.3}

 The sign or seal of God is the observance of the seventh-day Sabbath, the Lord's memorial of His work of creation. "The Lord spake unto Moses, saying, Speak thou also unto the children of Israel, saying, Verily My Sabbaths ye shall keep: for it is a sign between Me and you throughout your generations; that ye may know that I am the Lord that doth sanctify you" [Exodus 31:12-13]. Here the Sabbath is clearly defined as a sign between God and His people.
The mark of the beast is the observance of the first day of the week. This mark distinguishes those who acknowledge the supremacy of the papal authority, seen in the man of sin,--thinking to change times and laws,--and those who acknowledge the authority of God....
Manuscript 1, January 11, 1897, (see also 1MCP 14-15) 

  "The importance of the Sabbath as the memorial of creation is that it keeps ever present the true reason why worship is due to God," because he is the Creator, and we his creatures. "The Sabbath therefore lies at the very foundation of divine worship; for it teaches this great truth in the most impressive manner, and no other institution does this.

   The true ground of divine worship, not of that on the seventh day merely, but of all worship, is found in the distinction between the Creator and his creatures. This great fact can never become obsolete, and must never be forgotten." It was to keep this truth ever before the minds of men, that God instituted the Sabbath in Eden; and so long as the fact that he is our Creator continues to be a reason why we should worship him, so long the Sabbath will continue as its sign and memorial. Had the Sabbath been universally kept, man's thoughts and affections would have been led to the Creator as the object of reverence and worship, and there would never have been an idolater, an atheist, or an infidel. The keeping of the Sabbath is a sign of loyalty to the true God, "him that made heaven and earth, and the sea, and the fountains of waters." It follows that the message which commands men to worship God and keep his commandments, will especially call upon them to keep the fourth commandment. {GC88 437.2}

     In contrast to those who keep the commandments of God and have the faith of Jesus, the third angel points to another class, against whose errors a solemn and fearful warning is uttered: "If any man worship the beast and his image, and receive his mark in his forehead, or in his hand, the same shall drink of the wine of the wrath of God." [REV. 14:9, 10.] A correct interpretation of the symbols employed is necessary to an understanding of this message. What is represented by the beast, the image, the mark? 

     The line of prophecy in which these symbols are found, begins with Revelation 12, with the dragon that sought to destroy Christ at his birth.  The dragon is said to be Satan; [REV. 12:9.] he it was that moved upon Herod to put the Saviour to death. But the chief agent of Satan in making war upon Christ and his people during the first centuries of the Christian era, was the Roman Empire, in which paganism was the prevailing religion. Thus while the dragon, primarily, represents Satan, it is, in a secondary sense, a symbol of pagan Rome.

  "Heretofore those who presented the truths of the third angel's message have been often regarded as mere alarmists. . . . But as the question of enforcing Sunday observance is widely agitated, the event so long doubted and disbelieved is seen to be approaching, and the third message will produce an effect which it could not have had before." {RH, April 27, 1911 par. 18}

This advice is to be of real value to all who are to be brought into strait places. Nothing that shows defiance or that could be interpreted as maliciousness must be shown.--2MR 193, 194 (1898).

"The enforcement of Sunday-keeping on the part of Protestant churches is an enforcement of the worship of the Papacy--of the beast. Those who, understanding the claims of the fourth commandment, choose to observe the false instead of the true Sabbath, are thereby paying homage to that power by which alone it is commanded. . . . {RH, April 27, 1911 par. 22}

To defy the Sunday laws will but strengthen in their persecution the religious zealots who are seeking to enforce them. Give them no occasion to call you lawbreakers. . . . One does not receive the mark of the beast because he shows that he realizes the wisdom of keeping the peace by refraining from work that gives offense. . . . {LDE 140.1}
Sunday can be used for carrying forward various lines of work that will accomplish much for the Lord. On this day open-air meetings and cottage meetings can be held. House-to-house work can be done. Those who write can devote this day to writing their articles. Whenever it is possible, let religious services be held on Sunday. Make these meetings intensely interesting. Sing genuine revival hymns, and speak with power and assurance of the Saviour's love.--9T 232, 233 (1909)

"When Sunday observance shall be enforced by law, and the world shall be enlightened concerning the obligation of the true Sabbath, then whoever shall transgress the command of God, to obey a precept which has no higher authority than that of Rome, will thereby honor popery above God. . . . As men then reject the institution which God has declared to be the sign of his authority, and honor in its stead that which Rome has chosen as the token of her supremacy, they will thereby accept the sign of allegiance to Rome--'the mark of the beast.' And it is not until the issue is thus plainly set before the people, and they are brought to choose between the commandments of God and the commandments of men, that those who continue in transgression will receive 'the mark of the beast.'" {RH, April 27, 1911 par. 23}

Rome's Challenge to Protestants
THE CHRISTIAN SABBATH
THE GENUINE OFFSPRING OF THE UNION OF THE HOLY SPIRIT AND THE CATHOLIC CHURCH HIS SPOUSE. THE CLAIMS OF PROTESTANTISM TO ANY PART THEREIN PROVED TO BE GROUNDLESS, SELF-CONTRADICTORY, AND SUICIDAL

 "To receive this mark means to come to the same decision as the beast has done, and to advocate the same ideas, in direct opposition to the Word of God. . . . {RH, April 27, 1911 par. 25}
"If the light of truth has been presented to you, revealing the Sabbath of the fourth commandment, and showing that there is no foundation in the Word of God for Sunday observance, and yet you still cling to the false sabbath, refusing to keep holy the Sabbath which God calls 'my holy day,' you receive the mark of the beast. When does this take place?-- When you obey the decree that commands you to cease from labor on Sunday and worship God, while you know that there is not a word in the Bible showing Sunday to be other than a common working-day, you consent to receive the mark of the beast, and refuse the seal of God. If we receive this mark in our foreheads or in our hands, the judgments pronounced against the disobedient must fall upon us. But the seal of the living God is placed upon those who conscientiously keep the Sabbath of the Lord." {RH, April 27, 1911 par. 26}

The time is not far distant when the test will come to every soul. The mark of the beast will be urged upon us. Those who have step by step yielded to worldly demands, and conformed to worldly customs, will not find it a hard matter to yield to the powers that be, rather than subject themselves to derision, insult, threatened imprisonment, and death. The contest is between the commandments of God and the commandments of men." {RH, April 27, 1911 par. 28}

Sundaykeeping is not yet the mark of the beast, and will not be until the decree goes forth causing men to worship this idol sabbath. The time will come when this day will be the test, but that time has not come yet. 7BC 977 (1899).

On which side are we ranging ourselves?--on the side of the dragon, who was wroth with the woman, and went to make war with the remnant of her seed, who keep the commandments of God and have the testimony of Jesus Christ? "I saw three unclean spirits like frogs," writers John, "come out of the mouth of the dragon, and out of the mouth of the beast, and out of the mouth of the false prophet. For they are the spirits of devils, working miracles, which go forth unto the kings of the earth and of the whole world, to gather them to the battle of that great day of God Almighty" [Revelation 16:14].
On which side are you standing?--on the side of those that worship the beast and his image?

"The sins of Babylon will be laid open. The fearful results of a union of Church and State, the inroads of Spiritualism, the stealthy but rapid progress of the papal power,--all will be nmasked. By these solemn warnings the people will be stirred. Thousands upon thousands have never listened to words like these.In amazement they hear the testimony that Babylon is the church, fallen because of her errors and sins, because of her rejection of the truth sent to her from Heaven. The people go to their former teachers with the eager inquiry, Are these things so?

 The ministers present fables, prophesy smooth things, to soothe their fears, and quiet the awakened conscience. But many refuse to be satisfied with the mere authority of men, and demand a plain 'Thus saith the Lord.'The popular ministry, like the Pharisees of old, are filled with anger as their authority is questioned; they denounce the message as of Satan, and stir up the sin-loving multitudes to revile and persecute those who proclaim it. "As the controversy extends into new fields, and the minds of the people are called to God's down-trodden law, Satan is astir.

 The power attending the message only maddens those who oppose it. The clergy put forth almost superhuman efforts to shut away the light, lest it should shine upon their flocks. By every means at their command they endeavor to suppress the discussion of these vital questions. The church appeals to the strong arm of civil power, and in this work, papists are solicited to come to the help of Protestants. The movement for Sunday enforcement becomes more bold and decided. The law is invoked against commandment-keepers." Spirit of Prophecy, vol 4, p 424-425

In different parts of the earth, Satan will manifest himself among men as a majestic being of dazzling brightness, resembling the description of the Son of God given by John in the Revelation. [REV. 1:13-15.] The glory that surrounds him is unsurpassed by anything that mortal eyes have yet beheld. The shout of triumph rings out upon the air., "Christ has come! Christ has come!" The people prostrate themselves in adoration before him, while he lifts up his hands, and pronounces a blessing upon them, as Christ blessed his disciples when he was upon the earth.

 His voice is soft and subdued, yet full of melody. In gentle, compassionate tones he presents some of the same gracious, heavenly truths which the Saviour uttered; he heals the diseases of the people, and then, in his assumed character of Christ, he claims to have changed the Sabbath to Sunday, and commands all to hallow the day which he has blessed. He declares that those who persist in keeping holy the seventh day are blaspheming his name by refusing to listen to his angels sent to them with light and truth. This is the strong, almost overmastering delusion. Like the Samaritans who were deceived by Simon Magus, the multitudes, from the least to the greatest, give heed to these sorceries, saying, This is "the great power of God." [ACTS. 8:10.]  -Great Controversy 624.1

Satan will … accuse God's people as the cause of the fearful convulsions of nature and the strife and bloodshed among men which are desolating the earth. -Spirit of Prophecy Vol 4 p44

"In Revelation 14, men are called upon to worship the Creator; and the prophecy brings to view a class that, as the result of the threefold message, are keeping the commandments of God. One of these commandments points directly to God as the Creator. The fourth precept declares: "The seventh day is the Sabbath of the Lord thy God: . . . for in six days the Lord made heaven and earth, the sea, and all that in them is, and rested the seventh day: wherefore the Lord blessed the Sabbath day, and hallowed it." Exodus 20:10, 11. Concerning the Sabbath, the Lord says, further, that it is "a sign, . . . that ye may know that I am the Lord your God." Ezekiel 20:20. And the reason given is: "For in six days the Lord made heaven and earth, and on the seventh day He rested, and was refreshed." Exodus 31:17.

  Brethren and sisters, would that I might say something to awaken you to the importance of this time, the significance of the events that are now taking place. I point you to the aggressive movements now being made for the restriction of religious liberty. God's sanctified memorial has been torn down, and in its place a false sabbath, bearing no sanctity, stands before the world. And while the powers of darkness are stirring up the elements from beneath, the Lord God of heaven is sending power from above to meet the emergency by arousing His living agencies to exalt the law of heaven.

 Now, just now, is our time to work in foreign countries. As America, the land of religious liberty, shall unite with the papacy in forcing the conscience and compelling men to honor the false sabbath, the people of every country on the globe will be led to follow her example. Our people are not half awake to do all in their power, with the facilities within their reach, to extend the message of warning.  {6T 18.2}

3 frogs.... Dragon = Satan
Beast = Roman Catholicism (The whore)
False Prophet = Apostate Protestantism (Daughters of the whore)

Further study:http://www.remnantofgod.org/books/LDE/LDE10.htm

To defy the Sunday laws will but strengthen in their persecution the religious zealots who are seeking to enforce them. Give them no occasion to call you law-breakers. If they are left to rein up men who fear neither God nor man, the reining up will soon lose its novelty for them, and they will see that it is not consistent nor convenient for them to be strict in regard to the observance of Sunday. Keep right on with your missionary  work, with your Bibles in your hands, and the enemy will see that he has worsted his own cause. One does not receive the mark of the beast because he shows that he realizes the wisdom of keeping the peace by refraining from work that gives offense, doing at the same time a work of the highest importance.--Testimonies, vol. 9, p. 232. {ChS 163.4}

     When we devote Sunday to missionary work, the whip will be taken out of the hands of the arbitrary zealots who would be well pleased to humiliate Seventh-day Adventists. When they see that we employ ourselves on Sunday in visiting the people and opening the Scriptures to them, they will know that is useless for them to try to hinder our work by making Sunday laws.--Testimonies, vol. 9, pp. 232,233. {ChS 164.1}

     Sunday can be used for carrying forward various lines of work that will accomplish much for the Lord. On this day open-air meetings and cottage meetings can be held. House-to-house work can be done. Those who write can devote this day to writing their articles. Whenever it is possible, let religious services be held on Sunday. Make these meetings intensely interesting. Sing genuine revival hymns, and speak with power and assurance of the Saviour's love. Speak on temperance and on true religious experience. --Testimonies, vol. 9, p. 233. {ChS 164.2}

     Let the teachers in our schools devote Sunday to missionary effort. I was instructed that they would thus be able to defeat the purposes of the enemy. Let the teachers take the students with them to hold meetings for those who know not the truth. Thus they will accomplish much more that they could in any other way.--Testimonies, vol. 9, p. 233. {ChS 164.3}

And that no man might buy or sell, save he that had the mark, or the name of the beast, or the number of his name. Rev. 13:17.


     The time is coming when we cannot sell at any price. The decree will soon go forth prohibiting men to buy or sell of any man save him that hath the mark of the beast. {Mar 183.1}

     In the last great conflict of the controversy with Satan those who are loyal to God will see every earthly support cut off. Because they refuse to break His law in obedience to earthly powers, they will be forbidden to buy or sell. {Mar 183.2}

     Religious powers, allied to heaven by profession, and claiming to have the characteristics of a lamb, will show by their acts that they have the heart of a dragon and that they are instigated and controlled by Satan. The time is coming when God's people will feel the hand of persecution because they keep holy the seventh day. {Mar 183.3}

     There is a time coming when commandment-keepers can neither buy nor sell. Make haste to dig out your buried talents. If God has intrusted you with money, show yourselves faithful to your trust; unwrap your napkin, and send your talents to the exchangers, that when Christ shall come, He may receive His own with interest. In the last extremity, before this work shall close, thousands will be cheerfully laid upon the altar. Men and women will feel it a blessed privilege to share in the work of preparing souls to stand in the great day of God, and they will give hundreds as readily as dollars are given now. If the love of Christ were burning in the hearts of His professed people, we would see the same spirit manifested today. Did they but realize how near is the end of all work for the salvation of souls, they would sacrifice their possessions as freely as did the members of the early church. They would work for the advancement of God's cause as earnestly as worldly men labor to acquire riches. Tact and skill would be exercised, and earnest and unselfish labor put forth to acquire means, not to hoard, but to pour into the treasury of the Lord. {Mar 183.4}