Avoidance of aggrivating factors is #1. Then stretching the forearm extensors. Clear the Cx and radial n. glide. Use taping, ice, ultrasound - whatever you like to help decrease the inflammation. Start a graded eccentric exercise program to build up the muscles such that they are strong enough to handle the activity which initially bought it on.

Search Vincenzino - he's got some brilliant articles on Wikipedia reference-linktennis elbow. Especially the Masterclass from Manual Therapy.