*Listen to your body:
Just because the doctor may have given you the thumbs up on a certain exercise does not always mean that your body is ready to do it full out. Start with just going through the basic range of motion of the exercise with no added resistance, if that feels okay start to gradually increase the resistance. Pay attention to the signals that your body is sending. It will let you know that something is wrong (usually) long before you injure or re injure yourself.
*Don't take your pain killers right before you work out:
You need to be in tune with your body while you are recovering. If you are all doped up on medicine you will not be able to hear the sometimes subtle messages that your body is trying to send you. Not to mention the fact that if you are not even supposed to drive while on prescription pain killers, the weight room is probably not the safest place for you to be hanging out.
*R.I.C.E (Rest Ice Compression Elevation):This magical formula works like a charm for most (if not all) injuries. Try to apply at least one aspect of R.I.C.E. as soon as possible after working out, all the extra blood pumping will no doubt inflame the injured area, R.I.C.E. will return it to normal faster than almost any other method. Not to mention speeding up recovery.
*Watch your diet
I know this is not actually exercise related, but while you are injured it is more important than ever to eat right. Eating lots of veggies, lean protein, and tons of water will help you keep your fit physique while also helping your body to better regenerate cells, get rid of toxins, and heal faster.
*Take it Slow
Believe me, nobody wants to hit the ground running (so to speak) more than I do, but when it comes to recovery, you really need to take it slow. This will help your body better adjust to the new stresses of working out while in a weakened state, while also allowing you to be able to really listen, and watch for the warning signs that you are pushing it too hard.
*Work Range Of Motion and Stability Before Strength:
Do excercises with little to no resistance until you can work, pain free, through the range of motion. If you've had a hurt foot, or leg, practice standing on the one foot to help regain the tiny stabalizing muscles that are so crucial in day to day activities.
*Workout
Maybe for some of you this goes without saying, but unless your doctor has given you explicit orders to do absolutely nothing, you need to get out and, at least, move around a bit. Obviously I am not recommending you go from couch potato to marathoner on a broken leg, but go for a walk, do some push ups, anything to help get your blood pumping. Increased circulation will help you heal faster than almost any other single thing. That is why it's so important to get, even just a little bit, of activity in each day. Plus you will have the added benefits of fat loss and muscle gain so that when your injury is healed you will not have to start from scratch.
