I'm 25 years old now, and here is the advice I'd give myself at 22:
Stop chasing girls. You can't convince someone to like you. Focus on improving yourself, and your desires will follow.
Put the drink down. It has been exactly a year since I quit drinking alcohol, and I've never been happier. My only regret is I wish I'd quit earlier in life.
Chase your dream, not someone else's. Time is so precious. Don't waste yours helping someone else build their dream by working for them. When you give someone your time remember that you're giving someone else a chunk of your life. Pursue only what you love and what interests you. If you don't, you will be miserable.
Get rid of the video games. This one goes along with #3. Video games are the worst time waster of all. I spent hours sitting in front of my TV playing mindless games and what did I get out of it? NOTHING!
Read more. Knowledge is power, and there is no better way than acquiring useful knowledge than books. When I read, I'm in almost a meditative state of mind.
There are many more points I'd like to make, but these are the ones that come to mind.