make people laugh
Children have short memories. If their last memory of you involved them laughing, they'll consider you a friend. At school I was a humourless overachiever, and I got picked on for bringing people down without realising it. So it's good to know how to make people smile, and to make it happen as much as possible.

if you're going to be stupid, be careful
Being "experimental", as it were, involves a lot of risks. As long as you protect yourself against these risks beforehand, you'll be okay. Examples: if you're going to drink copious amounts, know the quickest route to the bathroom in case you puke. If you're going to skateboard off the roof Jackass-style, wear kneepads at least.

book-smarts are only half the story
You might know every word of every book in the library, but if you don't have street-smarts or people-smarts, then your time on this little planet is going to be very awkward indeed. The academic world can open a lot of metaphorical doors, but you need to be able to open real doors in the real world to get anywhere.

direct your anger anywhere but your fists
Violence resolves nothing in this life. Rage can be a truly useful emotion if channelled properly. Learning to temper your anger is hard, but it's worth it if you can make something more positive out of it than bloodying someone else's nose. Pacifism rocks.