It'll sound cliche, but you'll know a good Enchi when you see it. The best ones are unmistakable. Here is the best description of Enchi I've come across:

"To me an enchi is as much about color as it is about pattern. Good enchi's will have one or the other but great enchi's will have both, the classic reduced banded pattern and that awesome golden/rusty/caramel color that will only get better with age." - Freakie_frog

Here's a good eye candy Enchi thread: http://ball-pythons.net/forums/showt...2430-Enchi-Q-s