I believe in the 12 man pitching staff: 5 starters, 2 long relievers, 4 setup guys (2 righties and 2 lefties) and a closer.
For my bench I go with a catcher, a shortstop, a guy with bigtime speed to be used as a pinch runner, and then the 1 (AL) or 2 (NL) best available guys I can find to round it out (preferably one of them being a guy that can play 3-4 different poitions at least, like a 2B, 3B or CF).