God... it's been almost two years since my seventeenth. That's just frightening.
Remember not to... uh.... Try to..... Never....
Come to think of it I don't have any worthwhile advice to offer. Try not to get too drunk too often ( kills the brain cells and hurts the wallet ). Keep up with the whole 'reading' thing. Pass what they set you to pass in school but don't take it too seriously; remember most of your teachers are there because they couldn't think of anything else to do with their degree. Don't do anything desperately stupid like take up smoking. Try to find some of the answers but not to anything important; at seventeen you should be asking 'what's my favourite album and why' not 'what is death'.
( Ignore the above ).