How to tell which GPU is which?

Hi all, I wanted to know how you all deal with the confusion of how GPUs are labeled in various programs. I'm having an issue right now where one card is "stuck" at 300mhz core&mem. For this, and other reasons, it would be helpful to know which physical GPU is GPU0,1,2, etc.
Claymore, GPU-z, and WattTool seem to label the cards differently....I have a single 290 in this rig and it is GPU3 according to claymore and GPU0 according to GPU-z!