Get plenty of rest the night before your shoot.
THIS IS ESPECIALLY IMPORTANT: I have had clients (mainly women) come to a shoot starving because they did not want to eat thinking that this will balloon them up. It has been my experience that the exact opposite is true!
If you do not eat your senses dull and your body actually feels heavier. Trust me, it looks heavier too. I have seen that transfer onto film. On top of that you will end up having a hard time focusing. Your body needs food. So eat PLEASE! There is such a huge difference between the fed and the unfed.
It's very smart to drink a lot of water the week leading up to the shoot. Your skin will love it and your body will look very good. I have seen that by taking at least 1 liter per 50 lbs. of body weight, per day, works really well.