A thesis statement should clearly state the main argument of your paper as well as what evidence you will use to defend that argument. Although one sentence is ideal, it will probably take at 2-3 to articulate your argument well.
Spending some time creating an outline will help you to determine topic sentences, organize your evidence, and map out the course that your essay will follow. In other words, a detailed outline will all but write the paper for you.
Think of a paragraph as a miniature essay: it requires a topic sentence (a thesis), at least a few sentences that explore and clarify the topic sentence in greater detail with citations and specific examples (a body), and a closing sentence (conclusion) that summarizes your comments and observations on the topic while setting up a transition into the next paragraph.