To start, you need a large cutting board or other work surface, a very sharp fillet knife, a pair of kitchen shears… and a fish.
Make sure the fish is scaled and gutted first, and be sure to remove the gills.
Start by making sure your knife is sharp. I know I just mentioned this, but it is important. You will mangle your fish if your knife is not sharp. Armed with a sharp knife, remove the back fin first. You need to do this to let the fish lay flat when you are done; the back fin also has a set of bones in it you want to remove.
Do this by slicing gently on either side of the fin, all the way to the backbone. Tap the tip of your knife against the backbone when you do this. Gently pull out the fin.
Now remove the ribs. Start from the tail end of the fish, and put the tip of your knife against the backbone where the ribs begin. Slice the ribs free. Do this by slicing from the backbone towards the end of the ribs, gently pressing the knife upward against the ribs — this preserves most of the meat on the fish’s flanks. Do this on both sides.
Now you need to remove the backbone itself. Start by freeing the ends of the backbone from the fish’s body. Use the kitchen shears to snip the backbone right behind the head and right in front of the tail.
Use the knife to free the backbone from the meat. Be careful not to slice all the way up to the top of the fish and through the skin. When you get close to the fish’s head you will feel resistance: These are the fish’s pin bones.
In trout, herring, sardines and mackerel, these pin bones are small and insignificant. Leave them, as you won’t even notice they are there once you cook the fish. In bass, bluegills, crappies, perch and rock cod, you will want to use needle-nosed pliers or pin bone tweezers to remove them. If you are butterflying any large fish (larger than 18 inches or so) you will need to remove pin bones.
Do this on both sides. You will be left with a fish lying flat and the backbone sticking up in the air
To remove the backbone, use one hand to anchor the fish where it meets the backbone; I start at the tail end of the fish. Use the other hand to gently pull it straight up. As it comes free, use your fingers to keep the fish flat and to preserve as much meat as you can. Gently work your way up towards the head and the backbone should come free.
You now have a fish perfect for stuffing. I like to sew stuffed fish shut, but toothpicks works just fine.
If you want to pan fry the fish instead, remove the rest of the backbone near the tail as well as the head so the fish lies perfectly flat.