Rinse the tilapia off in cold water and hold it by the tail on a flat surface, like a cutting board. Hold a knife or spoon with your other hand and scrape it from the tail toward the head to remove the scales. Use moderate force and rotate the fish as you go, until all the scales are removed. Use the back of the knife if that is the tool you use.

Make slits along the fins with a boning knife. Make a 1/8-inch cut on either side of the fin in a V shape, then grasp the fin and pull it straight out. Any bones or tissues attached to the fin should come out with it.

Hold the fish by the tail and place a sharp knife at the tail end on the underside and penetrate the fish. Make a slit along the belly of the tilapia and stop when you reach the gill area.

Open the belly up with your fingers and pull out the innards. Wear a glove if you don't want to touch them with your bare hands. Pull out as much as you can, then use a spoon or knife to scrape out any of the innards you missed.

Rinse the inside of the fish under cold water until the water runs clear. Use your fingers to scoop out any innards that were left behind.

Continue cutting the tilapia into fillets if you don't want to cook the fish whole. Turn it on its side and make a slit behind the gills from the top to the bottom, about halfway through the fish. Slide the knife along the backbone toward the tail, freeing the fillet on that side. Turn it over and repeat the process on the other side.