It’s not the prettiest site in the world, but homephonewiring.com has awesome guides for just about anything you might want to do with your home phone service. I went looking for it because my Mom wanted me to wire her up an additional phone jack and the instructions worked perfectly! They also have step-by-step guides for wiring a second line, wiring a third line, and wiring a DSL splitter. Very handy stuff if you don’t mind hacking around a bit with these things.
Verizon wanted to charge more than $100 to come out and wire up the additional jack, but it’s really only about twenty minuets worth of work and all you need is a screwdriver and wire cutters! It’s amazing how much money you can save if you are just willing to try something yourself!