I agree re getting the bones right. Everything else can be added or upgraded later.
I'd also say 'walk' around the plan and work out where you are going to need things like light switches as well as just the number of power points.
How will you use a room? Where will you enter it from? Do certain lights need to be wired so they can be turned on from two different switches depending on the way you pass through the area (a hallway for example)?
Also, showers - put your taps where you can turn them on and get the water warm before you step in!