Practice, practice, practice. Seriously, I'd take slow-releasing carb meal before, ensure you have glucose drink/tabs on hand just in case and stay hydrated. Chexk your blood when you get the chance too, so you don't slip into hyp-mode, as these are fast, furious, physical sports where you can get consumed in the heat of the moment. Be safe and all the very best! Hope it goes well. As you will burn off blood glucose very quickly it may be worh having the odd swig of lucozade sports so you don't suddenly drop "off the radar" and also some quick release sports bars to nibble on should you be exerting yourself fully, but just when competing, obviously. Go get 'em!
Mart.