Not sure if this has been posted already, but Coach Lee Jae Bok has some really great badminton videos posted online. He covers everything from basics to advanced skills including smash, drops, clears, backhand, footwork, singles play, doubles rotation, and many more! You can check them out here: https://www.youtube.com/coachingbadminton
Noted. Thank you. (Not that I would not have seen them already --- twice) ;-) Check the "search" in this forum, you'll find even more diverse coaching stuff, from kids to pros, articles, pay per view sites and apps ...