Not too much. First you need to go here and read this-printing it off will be helpful as you can use it as a reference as you build:

http://sheldonbrown.com/wheelbuild.html

Then assuming you have the spokes, rims, nipples and hubs you want to use, you need a spoke wrench. It helps to have a truing stand, but I have built lots of wheels without one, just use the brake pads and your frame or fork.

Suggestions:

Make sure you lube the nipple/rim interface, and the spoke threads with grease or oil. Makes the build way easier.

Go slowly and carefully-don't rush, and everything will work out nicely. Wheel building is not rocket science, and it really isn't all that hard, despite the way most shops try to make it sound. I started building my own b/c the quality of handbuilts I got from a number of local shops was really bad. Even my first build was way better than what I was getting from Dukes, Sporting Life etc.


I do my final tensioning with an inflated tire on the rim, the air pressure actually slackens the spokes slightly. Even, high tension=strong reliable wheel.

I find rims with steel eyelets are easier to build (less friction between the nipple and rim, but it doesn't matter all that much.

Watch out for spoke twist as you bring the tension up. You will learn to feel it, and back off the nipples to release the twist.

Have fun!