1. Learn how to flamenco dance (I know that's a spanish dance but they teach it in Italy too and the community is great).
2. Go to the clubs, enjoy the fact that all you have to do to get a drink is be tall enough to see over the counter.
3. Go to museums, don't take all the amazing artwork for granted.
4. Take a long drive with some disposable cameras-- they will be out of film in five minutes.
5. (for florence): Go see a movie at the odeon, that theatre is amazing.
6. Take a tour of the Duomo.. again, bring a camera to take pics when you reach the top (only do this if you are NOT claustrophobic!!).
7. Go to a wine tasting event (no matter how old you are!)
8. Go out to dinner at a restaurant near the Ponte Vecchio with 8 or more friends. Don't leave the house until 9 and don't leave the restaurant until you are the only people left, which could be around one in the morning :).
9. Visit Piazzale Michelangelo. You will not be disappointed with the view.
10. Sit. Close your eyes. Breathe in. Enjoy the fact that you are in one of the most beautiful countries in the world.