I recommend brining both whole fish and fish fillets before smoking; the reaction of the salt and sugar with the flesh of the fish seems to yield a much moister and more flavorful result. The recipes that follow provide detailed brining instructions.
For fish fillets, drying is also crucial to getting that authentic smoked fish taste cherished by so many. Drying keeps the fatty oils on the inside of the fish and stops the moisture from seeping out. While drying, the fish forms a shiny glazed surface that is sticky to the touch. This is known as the pellicle, and it can take from one to two hours to form. Place the fish in a flat pan and refrigerate it while it is drying.