With lunges, heavy weight is not necessary for effective development. Aaron Marino of alpha m. says that his leg development is attributed to this exercise. Lunges are exceptional for the entire leg.
Aaron demonstrates the stationary lunge first. Remember to stay up on your toe as well as your knee doesn't come over the toe. To make the exercise more difficult, add dumbbells. Don't slam your knee into the ground. Another variation are walking lunges. The trick is to take deep steps (long strides). Tap your toe for stability and balance. You can also add weight to this exercise. You can also do a version on the Smith Machine, which Aaron demonstrates.