NoRacer - congrats on getting out to Greenbelt to give racing a go. Great place to learn the differences between riding your bike, riding your bike with a group (even a fast one), and riding with a number pinned on to jersey and a start/finish line. Wish I'd have started my racing over there, but didnt know about the series until well after I was demoralized by my 1st race experience.
I always tell folks not to worry much about placing or even finishing at Greenbelt. It's a training race, so use it to practice stuff. I'll use it to work on weaknesses or hone in on things I do well. For instance, I'm a pretty aggressive racer (impatient) and have a tendency to go with every move that goes off the front, or start my own. Result is I burn too many matches early. I'll go to Greenbelt and tell myself that I'm not leaving the pack until Mr. X does, or until we're 8 laps in, etc. Alternatively, sometimes I just want to attack on the hill or out of the sharp right turn every time through until I pop. Either way, if you can get there, it's a great way to spend a wednesday evening.