Start here
http://www.bikeforums.net/showthread...s-a-tip-or-two
The following excerpt is from the thread linked above...
1. Find some group rides, fast group rides. Sit in the back.
2. Don't get discouraged if/when you get dropped from those group rides.
3. Go back the following week and do the fast group ride again.
4. If you're dropped a 2nd time, repeat steps 2 & 3
5. Once you're comfortable with the group and pace (and vice versa), take some pulls.
6. Once you're comfortable taking pulls, try some attacks (if it's that kind of group ride).
7. Once you're comfortable with steps 5 & 6, it's time to enter a race.
8. At your first race, repeat steps 1-6, but substitute 'race' for 'group ride'.