If you are a human, then the biggest influence on your personality is your peer group. Choose your peers.

If you want to be better at math, surround yourself with mathematicians. If you want to be more productive, hang out with productive people. If you want to be outgoing or artistic or altruistic or polite or proactive or smart or just about anything else, find people who are better than you at that thing and become friends with them. The status-seeking conformity-loving parts of your mind will push you to become like them. (The incorrect but pithy version: "You are an average of the five people you spend the most time with.")

I've had a lot of success with this technique by going to the Less Wrong meetups in Boston, and by making a habit of attending any event where I'll be the stupidest person in the room (such as the average Less Wrong meetup).