This is how Gordon's of Orleans Street Restaurant in Baltimore, Maryland, does their crabs.
Steamed Crabs Maryland Style
1/2 lb. seafood seasoning
1/2 lb. salt (mix with seasoning)
2 doz. live blue crabs
1 pt. water or beer
1 pt. vinegar
Put water and vinegar in a 10-gallon pot. Place a layer of crabs on an elevated platform in the pot. Sprinkle each layer generously with seasoning mix. Put lid on pot and steam about 25 minutes.