I generally take a pipe about the size to fit into a tool box of 1" carpenters conduit (the thin metal stuff) that I can slide over the 3/8th ratchet if I need to get a stubborn bolt off.
If you know the car you're going to be picking parts off of, know the car, know the sizes, etc. I can take apart a 3800 with an 8, 10, 13, 15mm, and a 3/8th socket set pretty much.