Sunfish and crappie are called panfish because they fit nicely in a pan; the reason people know they fit in a pan is because they are good to eat!
Both sunfish and crappie have mild-flavored, white, flakey flesh that lends itself to a variety of preparations. They do not have a lot of fat or contain a lot of oil, so any cooking preparation used should be covered or cooked with added fat or oil. Marinades work well.
Boneless filets are generally broiled or fried (with or without breading); while fish that are gutted and still have the skin attached (either head on or headless) are generally grilled, baked or fried.
Grilling boneless filets can be tricky because they are generally thin and can easily over cook (or slip through the grate).
No matter which way you prepare them, it is hard to go wrong. Like all fish, panfish should be carefully cooked to avoid drying them out. Overcooking is easy to do, so they should be removed from the heat as soon as the flesh turns from a translucent color to opaque (white). It is done when it easily flakes. The fish will continue to cook even when removed from the heat. Because panfish have a mild flavor, adding your favorite spices is recommended. However, go easy on the spices so you do not overpower the flavor of the fish.