LP Steamers is the best crab house in the Federal Hill area, a no-frills operation with communal picnic tables covered in brown paper where you eat steamed blue crabs by hand. The crabs come piled on the table, heavily seasoned with Old Bay, and you eat them with a wooden mallet and a lot of patience. It is messy, it takes skill, and it is one of the most specifically Baltimore experiences available.
The right approach: order a dozen crabs, get a pitcher of National Bohemian beer (National Boh is Baltimore's local lager), and ask the person at the next table to show you how to crack a crab if you do not already know. This is what people from Baltimore eat at summer family gatherings, and this is where to experience it.