you know that puzzle were there are 2 boxes, one is empty, the other has $1,000 in it, and there are two people standing next to the boxes,one lies all the time, one never lies? well, you just need to ask person 1 "would person 2 say he is a lier" and then run over to person 2 and ask "is box one empty"

if they say the same thing, open box 2
if they dont say the same thing, open box 1