It really depends on how far you want to commute and how much you can afford. Places I would suggest is most of NOVA, Montgomery Co. Northwest DC, and some areas around the capital.
I would not look in Anacostia, or SE DC. They are trying to gentrify some of the bad areas, but still...
Farther away is Charles county and Howard. I can't comment on Charles (just driven though it) but I lived in Howard for three years and its kinda of boring. And Prince George's County is a shithole IMO.
Places to go:
Georgetown is very popular but also trendy as hell. Bethesda has some nice restaurants and bars. Alexandria and Arlington also have a solid nightlife. Adams Morgan is another one that is popular. Again it just depends on what you like: bars, dance clubs, live music, and etc.
You can also head up to Baltimore to go to the inner harbor or see Camden Yards.