Pranks for school camp?

Hey guys (and girls). im going to canberra in a few weeks for a school camp and i need good sneaky pranks. we are staying at a hotel. every year the girls (all girls school) who go to canberra have a prank war. this year its my turn to win the prank contest so i need the best pranks. fire me with every one you got. even things that could get me in serious trouble. thanks!