You can start at Inland Aquatics Online at
http://www.inlandaquatics.com. They have some stuff, they also sell things for Refugia. The concept, I believe, was brought to aquarium keeping by Walter Adey. His book is Dynamic Aquaria, a good book, but it doesn't discuss running a refugium in any more detail than does TRA if memory serves me right. There are also some articles in the library here, I believe, if you just search on refugium or refugia.
There should be lots of other stuff if you look around. Like you, I haven't found a lot of advice that gets into the nitty gritty details of running one. Some of the principles are:
1) don't put any predators in it. This includes hermits. Some say cleaner shrimp are good in a refugium (they produce plankton) others say they should be treated as a predator. Definately no fish.
2) try to get the thing setup so that you can gravity feed from your refugium into the main tank, rather than via a pump. This keeps the little critters that grow in the refugium from getting sliced and diced on their way to the tank.
3) If you keep macroalgae in it (some do, some don't) try running it on a reverse photoperiod to stabalize your overall system.
4) It helps to seed it with one of the kits available if you don't have a decent population of little critters in your tank.
Other than that, everyone seems to invent their own approach. Most everyone agrees they are a good thing, however, if you can afford the space, etc. I'm running a 30 gal. refugium on my 90, but it is pretty new, so I can't really comment on results.
Good luck.
-Jim
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No really, hon, this is the last thing I need for the tank!
