Now that you have decided, at least tentatively, what information you plan to present in your essay, you are ready to write your thesis statement.
Avoid announcing the thesis statement as if it were a thesis statement. In other words, avoid using phrases such as "The purpose of this paper is . . . . " or "In this paper, I will attempt to . . . ." Such phrases betray this paper to be the work of an amateur. If necessary, write the thesis statement that way the first time; it might help you determine, in fact, that this your thesis statement. But when you rewrite your paper, eliminate the bald assertion that this is your thesis statement and write the statement itself without that annoying, unnecessary preface.
How to Write a Thesis Statement | eHow
You should write your thesis statement based on one main idea. It has to be AMBIGUITY FREE thesis statement because an ambiguous thesis statement is highly likely to fail your all efforts. You have to write it in accordance with your examples and evidence you would use in your thesis.