Well Michele, since your tickets are for May, I would suggest getting in line a little earlier than midnight. The lines are going to start getting absolutely insane as the spring months go on, and if you want a decent seat inside the studio, prepare to spend a looooooong time out on the sidewalk. As stated in some of the other posts, there are a couple bathrooms available, but each have their own set of stipulations upon reaching them. First you can try the CVS a short ways down from the studio, but they unfortunately close long before the OOA (order of arrival) numbers are handed out. Second is a Mobil station that's a block or so down the street, but you have to buy something in order to gain the coveted key on a wooden block. Third is inside the bagel store right across from the sidewalk, but some people question the cleanliness.
Again, there are plenty of other posts on here already that can help you out. Mainly I brought lots of music on my mp3 player, made lots of friends out in the line, and tried to sleep in the chilly 40 degree night air. Your trip is going to be one of the most exciting times in your life, so enjoy the experience all you can! The line is one of the best parts!