Where can you purchase hard alcohol near the District of Columbia?

I just moved from California to the Washington DC area and I'm wondering what the local laws are for purchasing distilled spirits (like Vodka, Tequila, Rum, etc.). In CA you can get such things at grocery stores, Costco, and the like, but I know that the laws change from state to state. I've seen some liquor stores on the corners, but would prefer to go somewhere where I'm confident I'm not getting ripped off. Any suggestions?