While running Cat6 and RG6 cable around the house, we also decided to pre-wire for a whole-home audio setup. My prior home had speakers installed in several rooms and I really enjoyed being able to listen to music around the house and in the backyard, so we added a similar setup in the new house. There are enough interesting details around the audio pre-wire that I decided to address it seperately from the Cat5 and RG6 pre-wire.
Before we built the house I was already looking at options to distribute audio through the house. The audio is almost always distributed from the head end to all of the zones in the house, but volume controls are usually done one of two ways: and the volume can be controlled from a switch or knob on the wall. The basic setup is to have a hardware volume control mounted on the wall. The speaker wires then run from the head end to the volume control, and then from the volume control to the speakers. The other option is to wire the head end directly from the speakers and control the volume from the head end (which can be done either directly at the head end, or from in the room with some sort of electronic control that controls the head end, or even through some sort of iPhone based interface that can control the head end).
When getting your home pre-wired, you usually don't need to make this decision ahead of time though, the builders wire it for both. Once the location for the head-end and locations for all of the volume controls are chosen, then one 4-conductor wire is run from the head end to each of the volume control locations, and two, 2-conductor wires are run from each volume control to the speakers. In addition, a Cat5 cable is run from the head end to each volume control location. Now, if you want to use the hardware volume control on the wall, you wire the 4-conductor wire to the input side, and the 2-conductor wires to the output side and just disregard the Cat5 wire. If you want a more advanced electronic control, you simply grab some wire nuts and connect the 4-conductor wire directly to the 2-conductor wires (effectively wiring the speakers directly to the head end) and use the Cat5 wire for the electronic control.
One small change I made to this was the size of the low-voltage junction boxes the builder uses. I believe they usually use a single-box, but I had already known what system I was going to install which required a 2-gang box, so I had those installed instead.
As for the head end location, that was pretty simple in the new house. I had already set aside an equipment closet to house the media room rack and also the structured wiring cabinets. This is a natural location for the audio head end. In addition, the audio wires for the media room's 7.1 (with 2 coax runs for 2 subwoofers) pre-wire were also run to the same place.
I wired for 8 zones of audio through the home as well. If you're keeping count, that's seven 2-conductor wires, eight 4-conductor wires, eight Cat5 wires, and two coax wires for a total of 25 wires as well as a soft conduit to run. All of these wires were left behind the drywall with a 2-gang box installed for access.