I think of scallops as the tenderloin of the sea. When cooked properly, they are delicious. When over cooked, little good can be said of them.
Generally, there are only two kinds of scallops available, both coming from the Atlantic Ocean -- bay and sea scallops. Bay scallops are smaller, sea scallops are a pretty good size, just a hair more than a mouthful. Both are equally delicious.
There are three other categories scallops can be divided into: diver scallops are hand caught by divers, causing little environmental damage and tend to be of better quality; dredged scallops are harvested by dredge, just like our oysters are; and a final category are farmed scallops that come from British Columbia, another ecologically friendly method.
Scallops are hard to find. I do not recommend the frozen variety, with few other choices than a visit to your fish seller. They may have to be specially ordered, and they may come in bulk quantity (a gallon may be the smallest container). Your best bet is to get a few friends to split them with.
Cooking scallops is a simple matter. Allow them to come close to room temperature, dry them off and lightly season with salt and white pepper. Pour a little olive oil in a sauté pan, when the oil just starts to smoke carefully add the scallops, but do not over crowd the pan -- 1 and 1/2 minutes on a side and not 1 second more. They should still be a bit translucent in the center. Remove and serve at once, with just a garnish of fresh, sliced lemon, or a thinly sliced cucumber salad.