Always perform a good warm up before fast workouts and races where you will be starting at a high pace. Follow with a cool down.
Jog easy for 15 minutes. Start with walking, then move into slow jogging. Gradually increase the pace as you start feeling comfortable. The last few minutes can be run a good steady tempo.
Follow the jog with a few dynamic stretches.
Finish off with 3 to 5 stride outs over 50 to 100m.
Slowly jog, slowing down to a walk for 5 minutes. Finish off with stretching. Put on a warm jacket before cooling down. If your running gear is wet then change into dry clothes immediately after your session to minimize risk of falling ill.