College Application Essay: how do I write it?

I am in the process of applying to colleges, and most of them are crazy ambitious schools. I have above a 4.0 GPA and am a good student etc. so I think my chances of getting into to these schools are pretty decent. Nonetheless, I really want to stun the pants off of anyone who is going to read my application essay.

And I’m freaking.

I don’t really know what to write about. The majority of the advice that I’ve gotten is that I want to stand out, promote those things that make me, me. Additionally, a lot of people say that instead of writing about a broad subject (like how I forced my school to let me go to Sweden for 6 months), I should pick a specific event or moment that has really affected me.

My uncle who is a professor now wrote about what he learned sitting in a field.

HELP!