In order to debone a fish one should start from removing the scales. A lot of advice how to do it quickly and easily can be found at the webpage:

http://www.graal.pl/porady/jak-usunac-luski-z-ryby,item,6,12.php

Once you have removed the scales from a fish, you should prepare a flexible and long knife, which will simplify and quicken the whole process of deboning.

The first step is making a cut right behind gills and leading it up to the backbone (however, one should not cut off the head of a fish, because it will ease the next stages).

When we will feel the resistance of the backbone, we should turn the knife (with the blade in the direction of a tail of a fish) and gently move the cut along the back, to the tail of a fish. In this way we get the first prepared fillet.

In order to get a second fillet we turn over a fish and we repeat the cut right behind gills, until we feel the backbone and then we make a cut along the back, up to the tail.

This way of deboning a fish enables to get two fillets with a skin and the head together with the backbone.