Run the Water Lines
Once the holes are drilled, start running the water lines. In most cases, the lines will come through the floor. In some cases, the lines will have to be run across the wall studs. When running the pipes through the studs, first be sure to drill the holes in the center so that when it's time to hang the wall board, the screws or nails don't reach the pipes and damage the pipes.
Note: Take this extra precaution -- Ed recommends using a nail plate. The nail plate has tacks on both ends of a flat piece of steel. Line them up to cover screws or nails so they don't penetrate the steel to damage pipes.