If you’re like most, you more then likely train your legs all at once, this can be fine, but I've found that if you split up your leg training you can bring up the lagging area. For instance, personally my quads have always grown fast, probably better then any other muscle, in short they began to over-power my ham development. So what I've done for the past year is to train my quads and hams on separate days, that way I can give my full attention to both as well as 100% of my energy. After a year of this I feel my over-all leg development has vastly improved.
I've now gotten to the point to where I will most likely begin to train hams and quads together again and now I will use the day I used to train hams to help bring up another body part I feel that is lacking or that needs to "catch up" to the rest.