Many seafood dishes have the added bonus that they hardly require any time to make. Not taking into consideration the stuff that can be consumed raw, of course, cooking decent seafood calls for a good dose of common sense and a bit of skill. It's pretty much like cooking the perfect steak. Let's take salmon, for example- one of my favorite pieces of fish, and one which should be served moist, never cooked through. I recently had the misfortune of ordering pan-fried salmon with beurre blanc at a restaurant and ended up being sorely disappointed with what I got. So disappointed that I could've cried. Not because I had to send back the beurre blanc which tasted of spoiled milk, but because the second piece of fish (you read right) was also cooked to a dry, brick texture. Pure culinary barbarism.
Prawns, another favorite of mine, can also be easily overcooked. Depending on their size, I think anywhere from two to six minutes max should be enough. The point is for the prawns to retain their sweet taste and juicy flesh, not to make them tough and rubbery.
One of the nicest ways to cook prawns is with shallots, garlic, a good knob of butter and a shot of Pernod. Once done, I sprinkle them with plenty of fresh, chopped parsley and dill and serve them with thin slices of lemon, grilled tomatoes and good bread. You could, however, serve them over a bowl of cooked linguini. Prawns are very versatile and can handle a wide variety of seasonings. Just make sure you don't overcook them...