Do more races, the butterflies will go away with time
-As said above, no electronics 1 - 2 hours before
-Get bike, gear, food, directions everything ready 2 - 3 days in advance, make a checklist so there is nothing to occupy your mind the night before
-Load up the car/truck/van the night before also
-Mentally put a game plan together a day earlier too, breakfast, drive down, parking, registration, number plates, warmup, grid up, run the race.
-Melatonin is also a great sleep aid, may give you crazy dreams but will definitely knock you out