No limit Texas hold em: shall we talk about going all in?

I am interested to know, if you play texas hold em; if you are sat at a table and some moron keeps going all in every single hand before the flop, at what point do you call them? do you wait until you are in late position with a good set of pocket cards, do you attack them and challenge them to go all in if you are in early position, or do you check and wait for them to hang them selves.

additionally, with what pocket cards do you go all in pre-flop?