Insulating the garage

[Daox]

I had started a thread on heating my garage this winter. I guess that was a it premature as it still needs to be rewired (existing wiring leaves something to be desired) and insulated. It is standard 2x4 construction and I'd like to get as much insulation into it as possible. However, I'm unsure what the standard procedure is for garages. I'd like to get more than R13 or so fiberglass in there. I'm currently thinking that I'll put some rigid foam insulation over the fiberglass and then some OSB over the rigid foam insulation. I'm not sure how thick I can go, and this would also mess up electrical recepticals I'd imagine as they'd need to be moved outward to mount flush with the wall. I also don't know what I'd need (if anything) for vapor barrier.

Any advice or ideas are welcome.