Do you have any group riding experience? That's the first step. Get comfortable in the pack. Then, I'd say just enter a race. If you can get down to Freemont on Sundays the Early Bird Crit Series is great for beginners. The first clinic/race was yesterday, and they go on through the end of the month.
Don't get caught up in age groups... you will learn a lot more from the older folks and you'll be suprised how fast they are.