Depends on what you're shooting. If you're shooting something you'd have shot with a view camera in the old days, set up on a tripod, attach a cable release, go to mirror up, compose very, very carefully, and shoot several frames just in case something unexpected has intruded into the scene -- something you've missed. But if you're shooting something like the group of pool players I shot about an hour ago, shoot a whole bunch of frames, knowing you're going to dump most of them. In a group shot like that you can depend on somebody having his eyes closed in a few of the frames, and some guy with an incipient sneeze in one or two others, and a few others where somebody is putting on a "funny" face or just looking pissed, a face that doesn't fit with the others. In that kind of situation you can't really go back and re-shoot, so make sure you have what you need before you quit.