the doll face posted a question in the thread about the mystery dim sum place in NoVa, inquiring about a good place for newbies to try.
I'll second the suggestion asun made for New Fortune in Gaithersburg. The servers are usually good about explaining what's on their carts.
However, weekends are chaotic in any good dim sum place. If you're trying dim sum for the first time, and won't be accompanied by a veteran, a weekday outing might be the best option. Some places (like Oriental East) switch to menu service on weekdays, but others (like New Fortune) roll around the carts all week. You probably won't see unique dishes during the week, but all the standards should be available.
Try ordering 3-5 dishes per person. When I go solo I grab 6 or 7, but I'm greedy!
You can see photos of common dim sum dishes at:
The link below describes the basic dishes (and reviews some dim sum places in Atlanta).
When in doubt, start with har gow (translucent shrimp dumplings), sui mei (pork or pork/shrimp open-topped dumplings), baked or steamed BBQ pork buns (baked is bread-like and slightly sweet, steamed is fluffy), and a green veggie (usually there's Chinese broccoli).
I love chicken feet, but they freak out my husband. Thus the solo dim sum outings. :)