When dealing with automotive electrical systems, gorund is disconnected first, connected last. You really have to be carefull with that when dealing with any modern cars and any alternator using the Delco style solid state regulator (almost all aftermaket alternators are running that type). If you hook up the positive last, you will fry the regulator. If you hook the ground up first, when you hook up the hot side, you will be the ground when dealing with a automotive style electrical system.
