I use this as a guide:
Changing the pole piece height in your pickups can dramatically affect your sound, so I've created this guide to explain how to best set the pole piece height on standard humbucking pickups. This simple adjustment can do wonders to improve clarity and balance the string-to-string output of your...
www.mylespaul.com
but ultimately, I agree with this:
I use a standard set of measurements to "rough-in" then tweak by ear. Matching volume output of Neck and Bridge has to be done on the fly and by ear to get it perfectly right.
Also, string to string balance has to be done by ear as well.
As far as rough values? I typically go with 4/32" High E Side on Neck, 5/32" Low E Side on Neck and 2/32" High E Side on Bridge, 3/32" Low E Side on Bridge to start. My action is a touch higher than most i would say and since I own an Epiphone with short rings, I can;t use them as a "mile-marker" for height.