If you happen to catch more fish than you can eat or sell at one time, try hanging one for a day or two. This works better in a closed environment, like on a boat.
Cut off the head and pull out the organs. Tie a rope around the tail and hang it up out of the sun. Blood in meat generally tastes bad. A salmon spine can't take the force of being held by the tail without breaking, so make extra sure to bleed the fish if you intend to hang it. This is a red salmon after a day of hanging. Some people will just throw the fish on top of the cabin in the shade, but hanging it helps get more blood out.
Filleting a fish is generally easy if there is a head to hold on to, so hanging can make the fish hard to fillet. Maybe that means it's time to get a cleaver and do steak cuts.
Step 1: Cutting It Up and Eating It
cut it up. This is really a picture of fresh (30 mins old) salmon, but a fish that's hung out to dry looks almost as brilliant. Cutting up chunks and searing them in a curry is always a good bet. Use a sharp knife to get all the meat.
Step 2: Cook It
It generally tastes better with a little cooking. Whatever you do, don't cook it too long (no more than 10 minutes for a full fish, a couple minutes for little chunks). This rule applies well to every fish I've ever eaten.