Note: Because of my geographic region and time of year, I will be using a Tilapia. The cleaning of other fish may be more difficult or incur specific changes. For example, cleaning a Northern is much more difficult due to the amount and placement of their bones.
Step 1: Gather Materials
* Fillet Knife
* Cutting board (at least the length of the fish; double the length will work best)
* Bowl of Cold water
WARNING: The use of a sharp knife is dangerous, but a dull knife is even more dangerous. Make sure your knife is sharp and follow proper knife safety (http://busycooks.about.com/od/howtocook/a/kitchenknife_2.htm); always keep fingers out of the projection of the knife.
Step 2: Separate the Spine from the Fillet
a. Lay the fish on its side with the spine facing you.
b. Place your knife at a 45 degree angle, under the fin, at the point where the gills meet the body of the fish.
c. Make a downward cut that is about 1/2 of an inch deep or half the width of the fish. This cut should reach from the spine to the belly.