Before you start, you should gut and trim it. You then need to cut off the fins, close to the body, on the sides, on top and underneath, cut out the gills from the base on each side then scale it from the tail towards the head, using a scaling knife.
To fillet a fish correctly, make sure the knife blade is always in contact with the bones to avoid gashes in the fillets.
Finally, remove the pin bones from the fillets with tweezers or with a paring knife if the bones are large. Then just grab the bone with the tweezers and remove it by swivelling it.