When we first start learning riichi, we call too often. As we progress, most of us start swinging the other way and not calling enough.
There are plenty of Western mahjong players who will look down on a more open style (naki-majan) of play and see it as a sign of a beginner. This isn’t entirely fair. There are plenty of advanced players who call frequently. Partly it is down to your play style and there is a balance to be struck.
There are a few basic rules of thumb you can use to help you move toward that fine balance. Here are two I would like you to test your options before you call:
1) Calling gets you into tempai
2) If you have a shape that is not ideal with regards to efficiency, waits or shape, you should call
First of all, please unless it’s desperately needed, don’t try and push this into a half flush. It’s already mangan and with the right call, you could be sitting on a quick and easy win.
Calling and discarding the 北 will get you into tempai with 4 han so you complete the requirements for rule (1).
You have two options to call: with the 56 or the 89.
Calling with the 56 would leave you a 34 shape so only the 25s will complete your hand.
Whereas calling with the 89 will leave you a 34567 shape, waiting on the 258s to complete. This is a far improved shape with regard to wait and satisfying the requirements for rule (2) so you should definitely call.
(Example from Japan Professional Mahjong League “Mahjong Fundamentals Collection” p.79)