It's also important to ground as close as possible to where you're working so you have a short path.
PJG56: You're right. You may as well do both if you're doing one. Have you ever heard of clamping the negative and positive leads together after disconnecting them from the battery? I know some places do this as well but don't know why.
1982 Mercedes-Benz 300CD
1982 Mercedes-Benz 240D - stick