I have to write a Valedictorian speech for my upcoming graduation, and I am not quite sure what I should put in it.

Obviously I, as a High School senior, am in no position to be handing down advice or 'sage' wisdom to my peers, even though that seems to be the vast majority of graduation speeches. I also think it would be difficult to broadly summarize the school experience, as no two people's high school experience is quite the same. Right now, the only thing I know my speech should contain is some thank yous to teachers and parents, and that I should keep it brief.

What to you would make a good speech? What should I avoid? Realistically I know that no one is going to remember this speech in a few months time, but I would still like to put effort in and deliver a good one. My only concern is avoiding sounding like a pseudo intellectual and having a 'deep' speech.