Mike:
If you can keep your electrical load under 5 amps, you should be able to wire your layout in one section. 5 amps should be about 10 modern locos running at the same time.
However, you can;t rely on the rails to carry the current, especially through switches. Plan to run some thick wires under the layout to carry the main DCC load. Wire from this bus to the tracks at regular intervals, using a lighter wire. You have to wire to all parallel tracks.
You should add jumpers beyond any switches. Electrofrog switches will need the usual gaps beyond the frog to preven shorts, and then more jumpers. I don't think you can get any sort of reverse loop in 30", but these need extra wiring and a black box.
If you go for a walkaround control, you will need extra wiring for this. Usually telephone wires will do for this, but see the instructions. The Lenz system I worked with had telephone jacks or RJ45 every so often around the layout so you could follow the trains. If you are going to do major shunting or switching, you need a socket or two for each yard.
Hi guys im just going to start planning my new all away the room layout in size will be 40ft in 4 blocks of 10ft making at 10x10ft square with track room of 30inches width my problem is i like the new D C C set up but its not only and soley run on two wire is it so do u guys have a take on this deal i intent to run 6 lines a goods yard and shunting yards plus sidings so where do i need to isolate the points ect thanks in advance mike 
