What could I do to help my broken leg heal faster?

Let it rest. Let it rest - get a cast or a boot if recommended. There is nothing else that you need to do immediately. You may need to go to pt once the immobilizaiton is off or you may help the part of the affected limb by doing some exercises to help preserve its functionality, but this will not necessarily affect the healing process of the fracture.
Do not smoke. Smoking tobacco has been shown to interfere with bony healing-if you smoke, it's time to quit. Follow your treating doc's activity restrictions: early on you may not be allowed to put any weight on it; as you heal and you advance weight bearing this will actually stimulate the bone to heal (wait until doc clears you). If healing is delayed, a bone stimulator can help. Talk to your treating doc.