Boil some water and toss em in till they're nice and hot.
I used to work in a restaurant where they'd put them in plastic bags with some ice (they had small ice, but an ice cube works too) and just heat em up in the microwave. I don't do this often because the smell stinks up the whole house. LOL
There really is no secret to preparing them. You're only heating them up.
Enjoy!! We have some Alaskan Snow Crabs for tomorrow's dinner.