Fish is fresher if you buy the whole fish: the meat holds its shape and flavor better. It's cheaper, too. Here's what you need to know to choose this option for your menu:
1. For info on buying fresh fish (knowing its fresh, choosing the best fishmonger, etc.) Gorton's has a great site - complete with a printable info sheet to take with you to the store.
2. You will need four tools: a filleting knife (sharp, long, flexible); a chef's knife (large, sharp); a set of needle-nose pliers (tweezers will do in a pinch); and kitchen scissors.
3. You'll face two kinds of fish - round or flat. Preparation is a bit different for each type. (Gorton's explains this well, too.)
4. As for what you do, first, you "prepare" the fish. This involves cleaning it and removing the ooky parts.
5. Then you "fillet" it, which involves cutting away large portions of the meat away from the bone. Skin stays on at this point. If you have a big fish (think shark), you don't fillet: you "steak"... you "steak the fish".
6. The next steps are to "debone" and "skin" the fillets/steaks.
For detailed instructions on all these steps, check out Gortons.com, NoBonesAboutIt.com (they have videos), cutlery.com, foodnetwork.com (more video).