There's a saying in Italian: fritte son bone anche le scarpe, meaning "even a shoe tastes good when it's fried". Well, I couldn't agree more--and seafood tastes especially delicious when it's fried--good enough to convince even the piscatorially challenged.
There are several different ways to make fried fish. The simplest (and my personal favorite) is simply to cut up pieces of seafood and lightly coat them in flour seasoned with salt and pepper (and, if you like, a bit of paprika for color). Then deep fry them --I like to use light olive oil--until golden brown. The fritto misto pictured above was made with a light batter of flour, olive oil and enough water to make a cream-like mixture. Some batters call for adding egg to the batter, which you can add whole or, if you want to get fancy, add the yolk and then (just before frying) fold in the egg white, which you will have whipped into a foam. Egg batters, however, especially if you whip your egg whites, will be quite thick. You need to let any batter sit for about an hour before using. Make sure you're seafood is quite dry before coating with your batter, or the batter will tend to slip off in the frying.
How much you fry is a matter of taste. I like my fried foods 'medium', neither very dark nor very light. But follow your own preference. The main trick to frying is the correct temperature. You want the fish to fry until it is entirely cooked (but not overdone) inside and nice and crisp outside. If you fry the fish at too high a temperature, it will brown on the outside before it is fully cooked inside (although this is less of a problem if you cut the fish into small pieces). Conversely, if you cook the fish too slowly, it will tend to get soggy and greasy... and some seafood like calarmari will become quite rubbery if it's not cooked quickly. As in so many things culinary, practice makes perfect.
Sprinkle your fritto misto di mare with salt and serve with lemon wedges. It is important to serve fried foods as soon as possible after they're done, while they're still nice and hot and crispy. As they say in Naples, frijenno e magnanno--which, loosely translated, means "fry it and eat it!"
Finally, for the choice of seafood. The mixed fry pictured above features shrimp, calamari and scallops--a wonderful combination. In Italy, whole small fish (such as fresh sardines or the tiny fish known as paranza, which I have never found outside Italy) are also typically included. Small crabs (or even better, soft-shelled crabs) make for wonderful additions as well. But let your own taste be your guide.