Badminton Champion Milestones

In badminton, the most important thing is basic which many of the coach do not understand
what is basic. Basic is include footwork and handwork. With the correct handwork, accuracy will
increase and less mistake to be done. And with the correct footwork, movement will get smooth and faster.
How to define which is the correct basic?
So far, i din't see there is any standard basic in badminton, as long as the student can hit the shuttlecock is ok.
For anyone who has the problem in making lots of mistake, can send me a link on their video clip and i will try my best to give advise how to improve their skill in badminton.