If you do that a few times, she says, you won't be buying fish anymore. Some fish fillets come with the skin on, which many people find unappetizing. If so, ask that the skin be removed when you buy it or take it off after cooking. As a general rule, fish cooked on direct heat require 10 minutes per inch of thickness. Baking will take longer, and you should follow the instructions in a recipe until you get a feel for the time.
Fish is done when it is opaque and flakes easily at the touch of a knife or fork.
Armed with LaFray's insight and her cookbook, we returned on our own to Save on Seafood a few days later to buy fish for that night's taste test. Today's catch was different. There were no grouper chunks, the last red snapper fillets had just been snapped up, and the only flounder was previously frozen. After our initial dismay, we realized this is part of the fun of shopping a fish market. You never know what you'll find, but you can be assured that much of it came off a fisherman's boat in the last 24 hours.