I used to keep everything (monsters, NPCs, and even PCs) on 3x5 cards to speed play. Now I don't even bother giving NPCs numbers that they won't need. No skill points used out of combat, no attack bonus if they're a caster that is dead if they're resorting to a dagger, etc. For NPCs in towns reverse the process, and don't bother giving them any stats needed for combat.
Sometimes it falls apart and you hfind yourself needing something you didn't prep, but that sort of limited winging it usually isn't a problem.