Speed, speed, speed. Agility, agility. Strength, strength. Tackling, tackling. Vision, vision.
That's a roll/training guide compressed. What else do you want to know?

Seriously, ST guides are going to be hard because people have had success using all C's, all defensive players, and a combo of the two. I personally like a devoted unit of 2 DB's (one primary returner and the other as backup) for gunners, 1 safety primarily for punt coverages, and a handful of DE's. I'll steal a few guys from the O-line for wedges and punt blocking, but otherwise that's it. The most important thing for all devoted ST players is to get speed up and do it quickly.
Move this to the new Pee Wee forum and we can go in depth there.