I thought I share this document with those who need to teach the 21 Rally Point Scoring System to their athletes. Some key points include: (1) the order of the service based on the initial position of the players at the start of the game (2) trying to remember "who" you were serving to The source of the original document is from Badminton Canada but I found it not too clear. With some modifications and my personal observations, here is the revised document. Hope this helps! Cheers!