Des MacHale quotes:

The average human has one breast and one testicle.

Take some time to play around with segmentation. If you can pinpoint your best and worst customers it's well worth the time.

The reason for your poor projections is often right in front of you. Whether you are using statistical analysis or just an average, sometimes the way you are calculating your numbers doesn't make any sense. Sometimes it's best to get up, take a walk, and revisit your calculations later. I have returned to my work many times and said: "Why the hell would I calculate it like that?"

A bit ridiculous, but true. The moral of this story is to separate men and women when analyzing number of sexual organs.