Deciding on a ThesisWhat is a thesis?
Why is it important?
The thesis is your paper's controlling idea. Picture a person saying to you, "I don't have time to read your whole paper. Just tell me in one sentence what your main point is." Your answer--that one-sentence "in a nutshell" version of your whole paper--is the thesis.
Where does my thesis statement appear in the final version?
Before writing: Deciding on your thesis before you start the rough draft helps you know what you want to write about--what facts, arguments, examples to put in, what to leave out. If, for instance, you decided to write a paper with the thesis "My job is the best job that anyone could have," you would probably include very different examples than you would for a paper with the thesis "My job is the worst job that anyone could have." If you just start a "my job" paper without knowing what your main point is going to be, you won't have any guidance for what kinds of things to discuss and what kinds of things to leave out.
The St. Martin's Handbook suggests using the following as a preliminary thesis statement:
In this paper I plan to [explain/argue/demonstrate/analyze, etc.] for an audience of [.....] that [....] because [....].
So for the "my job" paper, you might start out with a preliminary thesis statement like the following:
"In this paper I plan to explain for an audience of human service employees that my job is the best job in the world because every day brings new challenges and new opportunities for growth."
A sentence like this will not actually appear in your essay. It is just for your own planning purposes. Thinking it through before you start writing the assignment makes sure that you know in your own mind what your main point is going to be.
During and after writing: As you are writing your first draft, and then later as you edit, it's a good idea to revisit your thesis statement frequently, to make sure you haven't drifted off course. Check the topic of each paragraph: does it fit logically within the thesis? Check the kinds of research/examples you use: does each item clearly validate your argument? Perhaps as you wrote the essay, you kept including information about things you do not like about your job. In that case, you need to go back and change your thesis, since maybe you don't have good evidence that it's the best job in the world.
Maybe nowhere. The "rule" you have probably heard about the thesis statement being the last sentence in the opening paragraph suggests one possible location, but only one of many. Some documents might start right in with a thesis statement as the first sentence. Some might postpone the thesis statement till the end. In other--longer and more complicated--kinds of assignments, there may be no one sentence that states the thesis, but instead the thesis is the general theme that the reader develops as she or he reads through the whole essay.
Therefore, while having a clear thesis ( = you and the reader both understand clearly what the main point of the writing is supposed to be) is essential to good writing, actually stating that thesis in an individual sentence at some particular location is not so important. The main thing to remember is that your introduction and your conclusion should connect to each other in theme, introducing and reinforcing your main focus.