Grandfather owned an east coast crab & seafood restaurant and cooked them one way. He would steam them until the color changes from grey to a white/red/orange. I've used his technique on crabs, lobstah's, crawdads, and shrimp.
While living on the west coast, we cooked them another way - just like lownslow recommends. Slow poaching. Mom use to say its because the shrimp on the west coast are different than the east.
I've cooked them on indirect heat (grill converted to a smoker). Great way is to skewar them raw with scallops. Mop with butter, fresh garlic and kosher salt a few hours before adding to a grill or smoker. Turn on low heat, no smoke until the color of the shrimp are white/red/orange. Mop every 15 or so minutes with the butter, fresh garlic and kosher salt.
Bottom line, as soon as the shrimp's color changes from grey to a white/red/orange take them off the heat or they will be rubber.