This is a great exercise for quad development. Find a step, box or something that has height you can step on. Step onto the object with one leg and push yourself up till your leg is fully extended. Then lower yourself controlled and do it again.
With your supporting leg on the ground can give a small kick off the ground to help get you up. However, try to use your working leg primarily.If the height you chose is too easy find something higher. The higher you go the harder the exercise will become.
This is also a great exercise to start building strength to hit the pistol squat.