Physically - do things that make you feel good - excercise/sports/dancing/mountain climbing - anything that gets your heart pumping and the endorphins flowing. If discipline is an issue go for the easy options - just do lots of them.
Socially - consider social activities such as voluntary work , social groups, holidays , visiting people, training courses.
Antony Robbins book Awaken The Giant within would be a great book for you to read - it will give you a brilliant kick start.
The Health of Your Self-Esteem // Current Amazon.co.uk: The Edge: the Power to Change Your Life Now [2cd + DVD]: Anthony Robbins: Music