New designers often wonder what parts on a UV Map correspond to what areas on the avatar.
When I'm working with a new map I usually have the same question.

This evening I decided that I needed some Long Straight Hair and I've never used that map before.

So I colored in the map in really bright and unmistakable color blocks and upload it to the avi to find out where it landed :D.

The results surprised me.
Pic 1 is the block image as I uploaded it to the hair.
Pic 2 is the colored blocks overlaid with the map set to 50% opacity, so you can see what I colored in and why.
Pic 3 is where it all ended up on my head.

I never expected the yellow and purple to be buried underneath the other much smaller blocks. And I also still don't know if the color is going to be rendered up and down or side to side, so on try 2 I'll put some arrows on it.

Cel