I also opt for the three line system. I used to use the fuel valves from DuBro and GP but they leak easily, especially after 1 season. They also seem very susceptable to dirt and the small size valves don't have dust caps.

The three-line system is simply (from top to bottom) 1. tank pressure 2. fuel fill 3. carb. If you are using a fuel tank with a rubber stopper, you can duel clunk it so you can suck fuel out as well as put it in; otherwise you have to flip you airplane over to defuel it. It's not a big deal and it 100% fool proof. I also like to color code my fuel tubing so I never mix them up. The package the fuel tank comes in should show you drawings and different configurations. Personally I like the Great Planes tanks or the Hayes tanks. I throw the tanks out that come with ARF's.