I usually try to sleep until at least 10 if possible, as I'm up until 4-5am. I'd say 9 is more realistic, and it's rare for me to get more than 4-5 hours a sleep at night (or in the morning, more accurately). If I wake up and it's still early, I will just lay there for a bit.
When I get up, I eat breakfast. Then I will usually start my hygiene regimen: bathroom, brush teeth, sponge bath/wipe off, wash face, change clothes, etc. Whatever I need to do to feel fresh, clean, and ready to face the day.
Then I will lounge for a few hours, sit in a chair or lay back down even, trying to use as little energy as possible. I try to graze/snack all day long, just forcing myself to cram as much in as possible without making myself sick. I won't get a lot of calories later in the day, so I try to get in as many as possible in the morning.
I also am constantly drinking water. If I'm thirsty, I chug. If I'm not thirsty, I sip. I am constantly aware of my hydration, and always have a water bottle with me. As soon as it's empty, my #1 priority is to refill it. I stop at a water station almost every time I pass one.
I bring a portable music player so I always have some tunes going. I might read a book, smoke some cheeba, have a conversation with my wife or a neighbor, play cards if there are enough people willing to play, or just lay back with my eyes closed and listen to my tunes and all of the wonderful ambient noise the campgrounds have to offer.
Sometimes neighbors will have cornhole, frisbee or beer pong, but I don't bring this stuff myself. One year I had a buddy who brought a hookah-- now that was an awesome way to kill time. Really bulky and inconvenient though to transport and keep burning.
Then I will have lunch around 1:30-2, plan out my day/schedule, and get my bag packed and ready for Centeroo. Checked and doublechecked, with all "goodies" secure and out of sight. When I'm in, I'm in, I don't come back to my camp later in the day, so I bring everything I need with me. This includes an umbrella, camelback, sunscreen, snacks, light jacket, and a towel to sit on. If I have some time left after packing, I may try to take a cat nap before heading into Centeroo.
tl;dr - Eat, Drink (WATER), Sleep. Not necessarily in that order.