The key to Bible interpretation, especially for the book of Revelation, is to have a consistent hermeneutic. Hermeneutics is the study of the principles of interpretation.
In other words, it is the way you interpret Scripture. A normal hermeneutic or normal interpretation of Scripture means that unless the verse or passage clearly indicates the author was using figurative language, it should be understood in its normal sense.
We are not to look for other meanings if the natural meaning of the sentence makes sense. Also, we are not to spiritualize Scripture by assigning meanings to words or phrases when it is clear the author, under the guidance of the Holy Spirit, meant it to be understood as it is written.
One example is Revelation 20. Many will assign various meanings to references to a thousand-year period. Yet, the language does not imply in any way that the references to the thousand years should be taken to mean anything other than a literal period of one thousand years.
A simple outline for the book of Revelation is found in Revelation 1:19. In the first chapter, the risen and exalted Christ is speaking to John. Christ tells John to “write, therefore, what you have seen, what is now and what will take place later.” The things John had already seen are recorded in chapter 1. The “things which are” -that were present in John’s day are recorded in chapters 2–3 the letters to the churches. The “things that will take place” (future things) are recorded in chapters 4–22.
Generally speaking, chapters 4–18 of Revelation deasl with God’s judgments on the people of the earth. These judgments are not for the church just as recorded in 1 Thessalonians 5:2, 9. Before the judgments begin, the church will have been removed from the earth in an event called the rapture -1 Thessalonians 4:13-18; 1 Corinthians 15:51-52. Chapters 4–18 describe a time of “Jacob’s trouble”—trouble for Israel Jeremiah 30:7; Daniel 9:12, 12:1. It is also a time when God will judge unbelievers for their rebellion against Him.
Chapter 19 describes Christ’s return with the church, the bride of Christ. He defeats the beast and the false prophet and casts them into the lake of fire. In Chapter 20, Christ has Satan bound and cast in the Abyss. Then Christ sets up His kingdom on earth that will last 1000 years. At the end of the 1000 years, Satan is released and he leads a rebellion against God. He is quickly defeated and also cast into the lake of fire. Then the final judgment occurs, the judgment for all unbelievers, when they too are cast into the lake of fire.
Chapters 21 and 22 describe what is referred to as the eternal state. In these chapters God tells us what eternity with Him will be like. The book of Revelation is understandable. God would not have given it to us if its meaning were entirely a mystery. The key to understanding the book of Revelation is to interpret it as literally as possible—it says what it means and means what it says.