What Bryan said is the essential part. When you pull a muscle its a combination of rest and the right threathment. So a bit of heating and relaxing next to movement. What can help you in the process of healing is moving and activating muscles arround your hamstring. What this will do is increase the bloodflow in your leg and thus your hamstring. The 'fresh' blood contains the cells that your body uses to repair itself. Why you shoudnt try to activate plus stress the injured muscle too much is because of the waste and injured mass of the muscle will heal slower when under stress. So movement yes, stress nope.

When the muscle is repaired its time to increase the stress on the muscle. This is a thing of doing it everyday to get all the rom and functionality back in it. So stretching, stress on the muscle and 'forcing' range of motion.

Hope this kind of clrearifies how you can get full use back.