Installing drainpipes and downspouts is key to an effective gutter system. The easiest way to cut a drainpipe is with a circular saw. Mark the pipe to the appropriate length, and make the cut on both sides.
One thing you need to consider when hanging a drainpipe is the amount of snow and ice that will accumulate during winter months. Often people will run downspouts all the way to the ground, but the pipes can easily be damaged by snow plows, shovels, etc., and can break or tear completely off the side of your home or building.
To avoid this, consider cutting the drainpipes short by a few feet. This will still allow the water to flow away from the foundation, and avoid problems in the winter months.