I stretch for some 5 minutes (the everyday routine), then run anything from 10' to 20' depending on how I feel and the temperature. I try to do some accelerations in the end to get the heart and lungs working at a close-to-race-rate.
If running on track (thus not too worried with getting to a good position on the starting line) I try to get 2 minutes to sit down, close my eyes and focus on the race ahead.