Besides regular throwing, JOBE exercises, and weight training(3lb to 5lb weights), you have to make sure your mechanics are good. No use to start throwing long toss with bad mechanics , you may take two steps backwards instread of going forward. If you have a good instructor in the area have him look at you and possibly video tape you as well.
I have personally seen great success with my young 13yr old.
We purchased the Thrive on Throwing DVD by Alan Jeager and also purchased his Yeager Bands. Look into those items and throw as much as possible. Take it easy at first then work your way up to throwing long toss about 2-3 times a week,
Before we got on Jaegers program the son would be sore for about 2- 3 days. Now he has normal soreness for 1 day and we are back to throwing on Day 2!
Good luck and take care of that arm!!!