Reading material
A Beginner’s Guide to Riichi Mahjong – For complete newcomers to riichi or mahjong in general, start here
Daina Chiba’s Riichi Book 1 (RB1) – This is considered by many to be essential reading if you want to better your game after understanding the baseline rules of riichi mahjong
Training Tools
Euophrys’ Efficiency Trainer – Practice and learn tile efficiency with this neat browser game. Wide range of options to choose from so you can really hone in on which part you need to brush up on
ea.ncu’s Mahjong Tools – This site features a score calculator, wait trainer and a score trainer. Great tools for transitioning from online play to in person play
Yaku/Scoring Cheat Sheet
Aranlyde’s Riichi Cheat Sheet – A well formated, easy to read cheat sheet including yaku list and scoring rundown. Trimmed and rescaled versions available here – 100% / 95% / 90% / 85%