Just adding to what kreativekat said, attending June orientation is not mandatory, but it is great to do for several reasons. Besides the obvious of getting to know the campus and the way things work, you get to talk to advisors and sign up for classes. Also, because by definition everyone attending is 99.8% likely to show up in August, it is a great way to meet a potential roommate.
Also, there is a program that starts a week before move-in called The NOLA Experience. A selected group (and by selected I mean there are only so many slots, and I think it is first come, first accepted but I cannot fully recall the criteria) is able to partake in one of several different tracks. You get to move in to the dorm early, then go on either some outdoor adventures in rural Louisiana, or do various things around the city like explore different cuisines and learn about New Orleans history. There is a charge for this and it does not take the place of orientation, but I bring it up because clearly it is a kind of secondary orientation, if you will.