Rule 1 Connect your ADSL router to the primary socket where the drop wire enters your house. Disconnect all internal wiring to other phone sockets. They create chaos.
Rule 2. Replace any fluorescent lighting. It's the 21st century and that old fashioned stuff interferes with wireless.
Rule 3. Don't forget that wireless also works vertically i.e. you can bridge between floors.
Rule 4. Wires that are visible will annoy your wife.
If you have a wireless music system then it may possibly be configured such that each speaker re-broadcasts the signal. I have one repeater in the hallway and the various speakers dotted around the house form a very effective wireless mesh system that gives universal coverage. If however you have a newbuild then proper cat.6 / fibre is a good idea if your kit will always be placed in a convenient location. Never forget rule #4