Here are some links:

http://www.cs.usu.edu/~watson/artemisiaca/bowstringhowto.htm

http://www.texasarchery.org/Documents/DiStefanoStrings/serving.html

You can probably find a few more by doing a google search. I use the same serving jig that the first link shows. You can probably do one without the jig, but it's a LOT easier with it.