A few things about jump-starting.

1. Avoid it in the first place, if at all possible. A 100% depleted battery will never perform properly again.

2. Remember that you're moving HUNDREDS of amps through a relatively small cable - as a result you need utterly SOLID metal-to-metal connections.

HEre's a good guide:
http://www.ext.nodak.edu/extpubs/ageng/safety/ae1021w.htm