To repeat others here, without more details of the issues encountered it's difficult to give specific advice.
That said, I have found the following resources valuable:
The free Wireless guide that Lectrosonics publishes. Lectrosonics, Inc-Wireless Microphone Systems Guide
On the Audio Systems Group website, Jim Brown has a number of useful articles on Wireless systems.
Go to the ProSoundWeb SR forums and search for messages by Henry Cohen. Search the TheatreSound archives for the same.
There are also a number of articles that can be found in the AES library, though these aren't free. Given the above resources, they are also probably redundant to some degree.
Vear & Spurling - Wireless Microphone Systems, an Overview. 2003
Somers - Obtaining the best performance from Wireless Micrphones. 1992
Frese - Wireless Microphone Systems with a High Channel Density. 1992
Jim, are you able to elaborate on just how much signal loss might be expected from a coiled cable? I guess I end up with one of two coils or LMR400 about 2ft in diameter relatively often. I don't normally have trouble getting systems to work, but maybe I can make them work a little better.
Matt, I have no memory of seeing a range specification in any wireless manual. Given the number of variables in system configuration and environmental RF conditions I would treat any such specification as nominal at best, and mostly worthless.