I really don't get nervous before a race. Running's a doddle on the nerves, compared to the one-on-one combat of judo I did as a youngster. In fact, as above, if there is one thing that pre-occupies me before the start, it's whether I've timed my last piss optimally. 
Night before/morning of the race = same routine as any other weekend, don't get pissed the night before, and make sure there's a good 2.5 - 3 hrs between breakfast and the start gun.
Edited: 13/10/2012 at 20:24