
Photo by David J. Fred.
Essentially, cable lacing involves running a thin cord (traditionally waxed linen, according to Wikipedia—though standard twine would work for most purposes) along the length of the cables you're running together, looping the cables together at regular intervals. When you need to break a few cords out of the group, just don't include them in the next loop down the line. Cable lacing often uses an overhand knot called a "marline hitch" to secure the cords at each interval; you can see the marline hitch in action here.

How To Lace Cable Harnesses [Dairiki.net via MetaFilter]