Don't make choices you'll regret.
Make sure you've saved money.
Don't act all high and mighty over minors just because you can legally go to jail now.
Remember, don't do stupid crap, because if you get caught, you'll have actual consequences.
Don't get too caught up in life; remember to breathe, and appreciate the little things. it'll do wonders for you mental health.
Take my advice with a grain of salt- I'm not even eighteen myself.