The most important aspect is temperature. The beer lines must be cold all the way to the faucet. You are creating what's called an "air cooled system." You can create the air shaft from PVC wrapped with insulation. The next item you'll need is an air blower:
http://www.micromatic.com/category.php?cid=271
The blower will circulate cold air in the air shaft you have created, keeping the beer line cold.
Mike Godwin, Micro Matic USA, Inc. Northridge, CA