We published a guide to this many years ago, and are pleased to see our diagrams all over the web. The guide can be found here - http://www.scotaudio.com/wiring

The most interesting thing is why a balanced signal is used to transmit low level audio. Any length of wire will be susceptible to pickup from any electromagnetic source in the vicinity - that's how your radio and TV get their channels. Trouble is, you don't want the local taxi service or noisy mains interfering with your microphone feed. That's why one audio signal is in phase (the actual audio signal), one is out of phase (the audio signal inverted), and a ground. Any noise picked up by the cable affects the in phase and out of phase the same, so when the out of phase is inverted and summed by the receiver, you're left with the original audio signal and the noise cancelling itself out.