Track events? Or field events?
Track events, good to station yourself at a bend that doesn't have the spectators as the background as it is very distracting. The bend will ensure that you will see the faces of the athletics easily--if if they are running in a bend during a relay event they will spread out pretty nicely.
Another spot to camp in is near the finishing line.
Contrary to what others may say, I feel that fill flash usage in a track event is perfectly all right. If it's an evening event, you can use the 2nd curtain sync to your advantage to take "trails".
A mid-to-telephoto zoom lens will be good to use. A fast lens will bring extra advantage to freeze the action. A fast film/high ISO setting is recommended to compensate slow lenses. Recommended shutter speed is ~1/250 or higher to freeze the action. You can try slower speeds if you want to achieve panning effects--but always be sure to keep your athletic's faces clear.
Set your focusing point to the centre focus, and try using pre-focus--the AI Servo may not be fast enough, but you can try.
Practice your panning and try shooting with both eyes open to be aware of when the athletics are coming into your viewfinder.
Sometimes a portrait format works better than landscape.
