You need to make each stitch so that it locks over the previous one, if you lace it the wrong way it will slip. A large curved blunt carpet needle is the best to use, but if you go to a sewing shop and buy a curved darning needle, and grind the point off it will work fine. Take a look at the very bottom of this link to see how to lay in the stitches:
http://www.dairiki.org/hammond/cable-lacing-howto/
You can do it in situ, so don't worry too much about making a forming board, these are really only for mass production. don't be put off by all the complicated looking stuff further up the page, the bottom 6 diagrams are all you need. This page also shows various ways of tying off. I used to use white waxed lacing twine, but can't find it anymore, but RS has a black lacing twine. Don't try using anything but genuine lacing twine though.
Also, make sure when you run your wiring to lay it in in neat bundles that run together, and have sufficient length to form into nice straight runs with right angle bends.
Good luck, neat well done lacing is a thing of beauty.
