What is the proper way to run earth ground under a layout? Should it run parallel to the tracks or would it be better to zig-zag it back and forth under the layout? Should it be one continuous wire or can you use multiple feeds all connected to earth ground?

I first tested with a wire along side of the track; however, when I rebuilt my layout, I placed the wire in a zig zag pattern between the homosote and the plywood with attachpoints on the edges of the wood about 12 inches apart. I also pig tail the wires from each level into a single wire going to my water pipe. Many wires are tied together. On an earlier layout it was just beneath the plywood and it worked as well using the zig zag pattern.