Two things you should know about electricity:
Turn the power off when changing lightbulbs. Otherwise you just might end up ramming your swearing finger straight into the socket and leaping around the room swearing in front of your astonished parents.

When connecting a car battery to a mains charger, correct procedure is to connect the negative terminal, then the positive terminal, then turn on the charger. Not to turn on the charger, grab both leads by the metal parts and attempt to connect both at once.
( MatJ LOOK, Fri 13 Feb 2009, 20:11, 2 replies)

Nope. Positive first.
Then if the second one accidently touches something, you don't have a short circuit.
(Richy_T hundreds if not thousands of dollars, Sat 14 Feb 2009, 2:44, closed)

Yes.
In a car the negative terminal is connected to the chassis of the car so you could catch a jolt if you had hold of some metal structural part and the positive lead when you connected it.

When charging it in isolation though, the terminal you connect first probably doesn't matter.
(Prof. Moriarty put his foot in it on, Sat 14 Feb 2009, 21:39, closed)