You have to be positive before playing your roles or before shooting for any modelling audition. You need to take actively part in everything and pay attention to your role. It shows that you are interested in everything that is happening around you and you are engaging yourself nicely.
Sleep is imperative as if you sleep well before your playing your roles then you will look fresh and bright. Having a good night sleep is important if you want to look better the next day. So do not sacrifice your sleep if you have something important scheduled up the next day.