Like I've said before, the evaluation of the running back position at the high school level, much like the wide receiver position, is often entirely based on speed and statistics. However, most good college programs will also look for qualities like quickness through the hole, run vision, pick and slide, good balance, and change of direction skills.
A player that is termed an "all-purpose back" with excellent size and power is the ideal prospect for most programs. It's very rare when you get a back that can do everything: run, catch, and even return if necessary. These guys are nightmare matchup players for opposing defenses, and they can change the face of an offense's personality.