Disconnect the negative first.
Connect the positive first.
That's the way you always do it.
While it technically doesn't matter, you do it this why because you'll have a short to ground if you connect the negative first and then you go yo put the positive on and your wrench touches something metal while it's on the positive post. Been there, done that. I don't forget which order anymore. If the negative is disconnected and you do this, nothing happens, there's no circuit to short.
Last edited by Joey P; 11-07-2012 at 09:36 PM.