Crab legs are sold frozen and already pre-cooked. They are categorized by how many legs it takes to make up a ten-pound increment. For example, crab legs that are listed as 6-9 count would be larger than ones that are 18-20 count.
Thaw the crab legs in the refrigerator overnight or by placing under cold, running water for several minutes. Either way, it is a good idea to rinse all parts underwater to remove any salty, brine taste.
There are several methods to cook crab legs. Keep in mind that the crab legs (if frozen) are already cooked and you are just reheating them. The two most common ways to cook crab are by boiling and steaming but other ways include baking and grilling.
Boiling: Fill a large pot half full of cold water and add a large pinch of salt along with any other seasonings that you would like. Bring the water to a boil then add the crab. Reduce the heat to medium and simmer for roughly 4-6 minutes. Remove the crab legs and let them drain any excess water before serving.
Steaming: Fill a large pot with a couple of inches of water and add a large pinch of salt along with any other seasonings (same as you would boiling). Bring the water to a boil and then insert your steam basket with crab legs in it. If the crab legs are too large for your steam basket, cut the legs at the joints with kitchen shears. Cover the pot and steam basket and cook the crab legs until they are heated through (5-10 minutes).
Baking: Preheat your oven to 350 degrees. Place the crab legs in a baking dish along with lemon slices and any other seasonings. Add an 1/8 inch of hot water to the bottom of the dish and then cover with aluminum foil. Bake at 350 degrees for 10 minutes or until heated through.
Grilling: Brush the crab legs with olive oil and place them on a medium-low heat grill (300 degrees). Grill for 5 minutes per side or until heated through.