Fish as firepower: when it comes to building muscle, fighting fat, and protecting your brain and heart from disease, there's no better way to arm yourself than by slapping a slab of fish onto your plate

* Don't get stuck

Always cook fish in a non-stick pan or skillet. It's the only way to be sure the fish won't stick while you're cooking.

* Never overtook your fillet. You'll ruin it.

Most fish should be cooked to no more than medium. Compared with other cuts of meat, fish contains very little fat and can dry out quickly if it's even the slightest bit overcooked. A good rule of thumb? Always allow fish to cook for 9 minutes per inch of thickness.

* Don't drown your fish in a marinade

I like to use marinades on all types of fish (salmon, tuna, swordfish, red snapper, even cod). The key is never to marinate fish for more than 10 minutes. Marinades always contain some kind of acid or salty component--such as soy sauce--and both of those can break down the texture of the fish over time, turning even the best fish into a stinking pile of mush.

* When in doubt, use a rub

Rubs add a great deal of flavor to fish, and most of the time the fish needs it. (Without spices, most fish is fairly flavorless.) The trick, though, is to apply the rub to only one side of the fish, not both, or you'll totally overwhelm the taste. And like marinades, rubs should be applied only right before cooking--otherwise you risk breaking down the texture of the meat.

TONIGHT

WHICH IS THE EASIER WAY TO BUY YOUR FISH?

MERCURY RISING

Because of high mercury levels, the EPA advises against eating shark and swordfish--if you're pregnant. We'll go out on a limb and assume you don't need to worry about that. But don't think you're in the clear just yet. Toxic levels of methyl mercury, which larger species of fish absorb from the water and from the algae and smaller fish they feed on, can also cause long-term neurological damage.

According to the data from the National Fisheries Institute, catfish, flounder, salmon, sardines, Pacific sole, haddock, tilapia, herring, mahimahi, and canned white light tuna are among the safest fish to eat. On the flip side, try to avoid or limit your intake of pollock, grouper, halibut, marlin, swordfish, shark, mackerel, tilefish, and canned white albacore tuna--all of which are more likely to be contaminated with mercury.

*** STEAKS VS, FILLETS ***

FISH STEAK

What it is: A cross-sectional slice of fish, usually 1 to 2 inches thick.

Pros: They're less expensive than most whole fish and have a meaty texture that's more appealing to fish-haters. Plus, the uniform thickness makes them supereasy to cook--just slap 'em on the grill.

Cons: Fish steaks spoil quickly and sometimes have bones. Steak-worthy: Salmon, tuna, and halibut.

FISH FILLET

What it is: A side of fish that has been cut away from the backbone.

Pros: These cuts of fish, which are usually bone-free, absorb flavor quickly from rubs and marinades. They're also one of the absolute easiest cuts of meat to cook. Whether you're poaching, grilling, broiling, baking, or sauteing, fillets are always appropriate.

Cons: Because they're thin, they're easy to overcook, and their delicate, flaky texture doesn't hold together well. Fillet-worthy- Grouper, tilapia, catfish, and sole.