“Fish is done the second that the tip of a thin-bladed knife passes through the thickest part with no resistance,” says Mark Bittman, author of How to Cook Everything: Bittman Takes on America's Chefs, www.amazon.com.

Thick, steaklike fish, such as swordfish, should pass a sight inspection before being brought to the table. Make a small cut in the center and take a peek inside, using a flashlight to shine direct light on the center. If the fish is translucent, it needs to cook longer, but if it is milky white or opaque, it’s good to go. Salmon should be a glossy — not chalky — orange, and tuna should look pink, like your tongue.

When dealing with medium to large shrimp, cook them for 3 minutes after the water starts boiling. (Smaller shrimp will take less time.) Soon the shrimp will turn from translucent to opaque and begin to float. Scoop them out when they come to the surface.