In your warm-up, make sure to build to an intensity that is faster than race pace. Why?
Studies have shown when an athlete went faster than race pace during the warm-up they actually used less oxygen and less energy during the race.
A favorite warm-up of the professional cycling squad Team Sky (and mine) is after 10-15 minutes of light intensity, perform a 5 minute progressive build from easy to above race pace, typically done in 1 minute increments.
Perform this workout within 30 minutes of your event:
Warm-up: 10-15 minutes easy
Build: 5 x 1 minute: 1′ @ 70% race pace (RP), 1′ @ 80% RP, 1′ @ 90% RP, 1’@ 100% RP, 1′ @ 105-110% RP