Re:Type of Exercise
Try to do exercises that don't require any weight lifting right now. You can do latter exercises. If not sure what that is try youtubeing it. It is intense and will get your legs moving in all types of different exercises. The elypictal would be a good start as well, that is like combing biking and running all together, and would be easier on your knees starting out. Of course intense pushups and situps are going to be a good one as well. Set up two ends 20 yards apart and do different things such as high knees, but kicks, frog hops, one legged jumps etc.
I hope this helped, good luck