Educators love to talk about thesis statements—myself included!—and about shaping your argument around your thesis. Indeed, it is true that everything in your essay should relate back to, or support, your thesis in some way. What we don’t always talk about enough is how hard this is, especially because sometimes you have to think your whole essay through, or even write a full first draft, before you know exactly what you’re arguing.
A good rule of thumb is this: if you can’t sum up your argument in one simple, declarative sentence, then your argument isn’t clear enough. Keep thinking. Keep writing. Keep re-drafting.
Essays are just like punting... It's important to know where you're headed!