Use blocks in your loops, isolating the center rail. No more than about 10 track joints per block. One power feed per block to center and outside rail. Center of block is recommended for power drop connections. Depending on power requirements and power supplies being used, you may want to consider isolating your loops as well. Some decisions depend on layout size, power supplies, and what you will be running on your layout.
I think that's the main parts of it, but I probably forgot something. Maybe others will be along to add to this.