The teacher who wrote the book your mother probably owns.
Elaine Sandberg was a teacher first and an author second, and her book, A Beginner's Guide to American Mah Jongg, has been the first step for more new players than anyone can count. It teaches the beginning with patience, in the order a real player needs it: the Charleston before the card, the card before the hand, the hand before the defense. Her beginners come away oriented rather than overwhelmed.
Elaine passed several years ago, and Prim wrote about her on the Thursday before Mother's Day, because her book has become part of how this game passes from one generation to the next. "My mother taught me from Sandberg," people say. The book is still in print and still handed to nervous newcomers, and Prim's suggestion stands: give a copy to someone new, with a note inside about who first taught you.
Written from what the letter said. Read the letter for the whole of it.