I'm in VA so I can't advise you as to where to go in MD, but agree with PP that good starts are your local farmer's market and looking into a CSA. There might also be a co-op up in your area, I think.
Figure out what's most important to you. Is it local food? Is it organic or pesticide/hormone-free food? If you don't have an unlimited budget, what are your priorities?
I'd say start by just browsing your local farmer's market every week. Occasionally buy something that looks good. Say hi to the farmer. After a few weeks, I've found that they recognize repeat customers. You can slowly figure out if you like that farmer, their produce and prices.
We go to the Farmer's market in Falls Church and can buy almost everything - fruit, veggies, dairy, bison, beef, chicken, pork, baked goods (both to take home and on the spot croissants and crepes), homemade sausage, pasta and salsa, fresh flowers, homemade soaps and dog biscuits and wine.
This looks like the webpage for your local farmer's market:
http://freshfarmmarkets.org/farmers_markets/markets/silver_spring.php
It's fun to explore!