I actually use the stat block method. It fits everything into it in a fairly tight space. You can take this and just cut out what you don't want. I used to make all my NPCs in a MM type block, but it takes up a lot more room and I like to print out my NPCs that will be encountered together on a single sheet of paper. Here's an example I just copied and pasted.
Biddleporp: Male Halfling, Wizard (Enchanter) 3; CR 3; Small Humanoid (halfling); HD 3d4+3; hp 10; Init +3; Spd 20 ft.; AC 13 (touch 13, flat-footed 10); BAB/Grp: +1/-5; AL Neutral; SV Fort+3, Reflex +5, Will +4; Abil Str 6 Dex 16 Con 13 Int 15 Wis 10 Cha 12.
Skills and Feats: Concentration +10, Move Silently +5, Hide +7, Spellcraft +8; Skill Focus (Concentration), Spell Focus (enchantment).
Spells Prepared (4/3+1/1+1; base DC = 12 + spell level): 0th – detect magic (2), message, light; 1st – hypnotism, silent image, magic missile, mage armor, shield ; 2nd – daze monster, protection from arrows.
Alternately, sometimes I just throw together an index card with some stats on it. I'm fairly thorough, though. Blame the OCD.
