Mark out the path to your power pack location. On our layout that will be near the tunnel on the outside of the track. Use a razor blade or X-acto knife to cut a "V" shaped groove. Lay some 2 conductor wire to all the locations of your buildings. Use one continuous piece, but leave a loop where each building will be. This way you can tap into it later. Hold it in place with some small staples. Do the same for track and turnout power.