Cleaning Fish
Your fishmonger will clean the fish for you, but you should at least know the essentials:
Cut off all the fins.
Scale the fish by running a blunt knife from the tail to the head.
Slit open the belly and remove the intestines. Some fish (trout, for example) have a blood sac running along the backbone, so scrape this out with the point of a knife.
Rinse well under cold water and thoroughly dry.
(I like to leave the head on, but this is a matter of preference.)