Fish, the cook's friend, is best done simply

Many people shy away from buying fish because they don't know what to choose, where to buy, or how to prepare it.

But fish is quick-cooking and takes best to simple preparations, seasoned with no more than a squeeze of fresh lemon, a drizzle of olive oil, a sprinkle of sea salt, and grindings of black pepper.

Be flexible: Buy the fish that looks most alive. Allow three-quarters of a pound per serving for whole fish (the smaller the fish, the lower the proportion of meat); 10 ounces for pan-dressed fish (head and tail removed); one-half pound for bone-in fish steaks such as halibut and salmon; and 5 ounces for fillets such as flounder and sea bass.

Try a fish you've never heard of, such as triggerfish or tripletail, in a restaurant. Once considered a trash fish, firm, white-fleshed skate wings are for sale at Asian markets such as Assi and H-Mart, as are porgy (a sea bream prized by Europeans who pay a high price for similar fish at home) and the bony but tasty croakers (in the drum family like the red drum made wildly popular, in its blackened form, by Paul Prudhomme).

For the home cook, frozen fish can be a good, less expensive choice. Because of advances in technology, top quality "frozen-at-sea" (F.A.S.) fish is flash-frozen at very low temperatures in as little as three seconds on board ship. Look for individual portions of wild sockeye salmon and swordfish at Trader Joe's, two-pound bags of frozen sockeye salmon at Costco, or, at Assi, the fillets of super-frozen hamachi from Japan suitable for sushi. If you're still reluctant to buy frozen fish, keep in mind that most of America's sushi fish, in accordance with FDA regulations, has been frozen to kill parasites; only tuna and farmed salmon are exempt.

Fifty percent of the seafood and 75 percent of the salmon Americans eat is now farmed. From the cook's point of view, farmed fish tend to be softer and blander, though also less expensive, than equivalent wild fish. Respected environmental organizations including the Monterey Bay Aquarium's Seafood Watch put farmed salmon on their "red list" of fish not to buy, but it is, nonetheless, commonly available, high in beneficial omega 3 oils, and reasonably priced. Search out better-quality branded farmed salmon such as the excellent Black Pearl salmon at Dreshertown Shop 'n Bag.

Farm-raised mussels are an excellent choice and no longer restricted to "red sauce" Italian neighborhood joints. These inexpensive shellfish come in two-pound bags, cleaned and ready to cook Indian style with curry, Spanish style with saffron, Belgian style with white wine and garlic, or Italian style in red sauce. Cold weather is scallop time - but be sure to buy natural, untreated scallops, which will range in color from tan to pale orange. Pure white scallops have usually been chemically treated and, though less expensive, will lose much of their weight as soon as they hit the frying pan. Atlantic shad are in season now. Because of their complicated bone structure, it takes an expert to bone a shad. Shad is high in omega 3s, and its roe is a delicacy that deserves to have a comeback.