Shrimp will also continue cooking after they've been removed from the boiling water, so a cook needs to consider that fact, too.
But you don't just plop a brick of frozen shrimp into plain water. You have to season it. Most seasoning companies sell bags of crab and/or shrimp boil and these are great for seasoning. Add this to the pot of boiling water, along with a bay leaf, lemon slices, salt and a teaspoon or so of black peppercorns.
If you're shelling the shrimp before serving it, keep the boiling water and the shells and tails and return them to the water for about 20 minutes. Strain the water and you've got great shrimp stock, which can be frozen for later use.