Always seek the freshest fish in your local area. Ask your fish market or grocery if they receive their fish daily or what frozen options they recommend.
Ask about the origin of the fish you're buying, and make sure it has been stored at about 28F at all times, no matter where it came from.
If a fish smells "fishy," don't buy it and don't eat it. Look for shiny skin and undamaged scales. Press firmly on the skin and make sure the fish regains its original shape quickly. Whole fish should have clear eyes, not cloudy.
Purchase wood grilling planks from a gourmet food shop that are 1/4-inch thick and large enough for the fish. Do not use wood or shingles purchased from a home improvement store because they are chemically-treated and not food-safe.
Soak the planks in water for three hours; this allows the wood to smoke and smolder without igniting on the grill. If the plank begins to flame on the grill, spray it with water.
Skin-on fish like salmon cook best on a plank. If the filet has skin on, cut a few 1-inch slits (about 1/4-inch deep) on the skin side, season the filet and place on the plank. Grill at 450F on medium-high flame, covered, for 9-13 minutes (cook to an internal temperature of 135-140F).