7 +/- 2; no more than 3x if it's magical

Here's a link to a cool blogpost at Delta's D&D Hotspot about the limitations to how our minds process information, and how those limits should be applied to RPGs. It's good advice, and I plan on heeding it in my own future designs. In a nutshell...

• The human mind can evaluate (and store in short term memory) between 5 and 9 parcels of information at a time. More than that leads to analysis paralysis (or just forgetting things).
• Therefore, no single step in character creation should include a choice between more than 5-9 alternatives.
• Likewise, no single die roll should ever have more than 5-9 modifiers.
• The more complicated the parcels, the fewer you can handle, and the exact limit varies a bit from person to person. So, to handle the lowest common denominator effect, you should really read "5-9" as "5, maybe 6 if it's fairly simple".
• Another, largely unrelated property of the human mind is that we tend to think of things as: one-time unique event, two-time coincidence, and three-times means there's a pattern.
• As a result, things that you want to feel exceptional or magical shouldn't happen more than twice in any single game session. If you can cast that spell 4 times per session, it no longer feels special.
• An exception would be things that happen 3 times, but with a long pause between the second and third iterations. Like a recurring joke in a movie, when the long-delay third riff occurs, you laugh heartily and say "I shoulda seen that coming!"

Okay, so that wasn't a nutshell - it was 7 nutshells, coming from 2 different nut-trees. But, as a result, it was still just short enough for you to grok the point. (Well, most of you, anyway)