Add equal parts beer and vinegar to the bottom of a large steamer pot, about 1 inch.
Bring the liquid to a boil, then add a single layer of live crabs. Be careful, they'll put up a fight!
Sprinkle the crabs liberally with Old Bay seasoning, then repeat with 2-3 more layers of crabs, but no more than 4 total. Make sure the liquid is at a rolling boil.
Cover and steam for about 8-12 minutes, depending on size. Larger crabs (#1's) will take 12 minutes, slightly smaller crabs (#2's) about 10 minutes, and smaller crabs about 8 minutes. Set a timer.
Line a big table with newspaper or brown paper bags, then dump the steamed crabs out on top. Repeat with the rest of your crabs until they're all used up.
Serve immediately with extra old bay, melted butter, corn on the cob and plenty of ice cold beer