It's midweek and you weren't planning on a crab dinner till the weekend, but you just got a call from an old friend who's in town. What does it take to prepare that frozen crab in your freezer?

It depends on whether you have thawed it or not.

Ideally, thaw frozen crab before you pop it into that boiling cauldron. The best way to thaw crab is to leave it in the refrigerator overnight, but if you are preparing a last-minute meal, just put the crab legs into a colander and run cool water over them for a few minutes.

You can also cook frozen crab legs fully frozen; it just takes a little longer.

There's not a consensus among chefs on whether steaming or boiling is the best. For example, Better Homes and Gardens promotes boiling as the best option, because water can get inside the shells and keep the meat nice and moist. On the other hand, What's Cooking America recommends steaming, because crab meat's flavor is so delicate that boiling it can destroy the taste.

But let's assume you are boiling it. How long it should boil depends on the size of the legs.

Your market may sell either Alaskan king crab or snow crab from the North Atlantic and North Pacific oceans. King crab is larger, so it takes longer to cook.

Boil frozen snow crab legs for 8 to 9 minutes. Bring a large pot of water to a strong boil before dropping in the crab. Cover the pot; bring it back to a gentle simmer, and let it cook for 8 to 9 minutes. If the crab is fully thawed, 4 to 5 minutes is sufficient.

Boil king crab for approximately 10 minutes if thawed, and a few minutes longer if frozen.

Frozen snow crab or king crab legs, the larger varieties, that you find in the market have been precooked. In fact, they are usually cooked right on the boat within minutes of being caught and then are instantly frozen, so they are as fresh as possible. Precooked crab leg shells have a pink cast.

If you live in a coastal area and it's crab season, you will likely find live crab at your local fish market. Vendors do not sell dead, fresh crab because it doesn't keep and gets mushy quickly.