Take water. Drink lots before you go and take some out in the field with you, hydration means a better game, less likely to get grumpy and helps ease the aches and pains that come with running around like a lune all day.
in addition to bigsheps idea, DONT FORGET TO PEE! lol have fun mate, im going for my like, 10th time tomorrow but its my first time at the Mall in Reading