Your thesis statement is the culmination of all the reading, evaluating, thinking and insights. Every sentence in your paper should somehow build or contribute to your thesis statement.
"Do not worry. You have always written before and you will write now. All you have to do is write one true sentence. Write the truest sentence that you know." -Earnest Hemingway, A Moveable Feast*
Once you've decided what you will argue in response to your research question, it's time to write your thesis statement. This marks the transitional point between research and writing. You will want to articulate what you will argue and frame your paper for the reader. Here are some points to keep in mind, from The Purdue OWL:
Mention only what you will cover in your paper, and make sure it's supported by evidence.
Thesis statements usually appear at the end of the paper's introductory paragraph.
Your thesis statement is not etched in stone. As you write, you may find that your scope or angle changes a bit. Be prepared to revise your thesis statement accordingly.
*Hemingway, E. (1964). A moveable feast. New York, NY: Scribner.
Tips and examples for writing thesis statements - The Purdue Online Writing Lab (OWL) provides some excellent tips on crafting the thesis statement.
How to write a thesis statement - This guide from Indiana University at Bloomington provides another take on how to conduct the thesis writing process.
Thesis statements - The Writing Center at the University of North Carolina at Chapel Hill has also created an exhaustive guide to writing thesis statements.