Judgment Materials
Should you push, or should you fold?
Let us list the main factors you should use when making that decision.
How Likely Your Own Hand Is to Win
Naturally, it is not a good bargain to push with a hand that has almost no realistic chance to win.
Example 1
Riichi 
Hand 
Draw 
You were aiming for Kokushi Musou, and then someone declared riichi. (Example 1)
Even by feel alone, you can tell that pushing this hand would be a big loss.
The chance of even reaching tenpai, much less winning, is far too low.
Example 2
Riichi
Hand 
Draw
In Example 2, this is obviously a hand you should fight with. The correct answer is riichi after cutting 
.
You absolutely must not get scared of an ankou-suji possibility and declare riichi after cutting 
instead.
There is nowhere near enough evidence to conclude that the opponent must be waiting on 
.
That choice would only slash your own winning chances and become the worst possible play.
If the hand looks likely to win, you push.
That is the most basic rule of push/fold judgment.
Point Value
The higher your own hand's value, the more naturally it becomes worth fighting with.
Example 3
Riichi
Hand 
Pon 
Draw 
For example, if the dora here is , then folding is the safer choice.
There is no point in taking a head-on fight with only a 1000-point hand.
However, if the dora is 
, then this obviously becomes a hand you should fight with.
You can keep pushing without hesitation until the hand is close to exhaustive draw.
Factors 1 and 2 both measure the return you can expect by taking the fight.
Of course, at the same time, you also need to understand the risk that comes with fighting.
How Dangerous the Tile Is
Estimate how dangerous the tile is that you would normally cut if there were no riichi on the table.
Naturally, if the tile is not very dangerous, you should fight.
If it is dangerous, you should start thinking about folding.
Example 4
Riichi 
Hand 
Draw 
When I say "danger level," I am not asking for advanced reading.
In Example 4, all you really need to do is estimate the danger of 
.
Since 
has already passed, it can only hit a shanpon or tanki wait.
The risk is low, and a tile like this is fine to cut.
You may or may not continue pushing after this,
but at the very least, this is not yet the point where you should choose to fold.
The Opponent's Estimated Point Value
Naturally, you do not want to challenge a riichi that looks very expensive.
But trying to estimate the exact value of a riichi from the discard pond is extremely difficult.
Unless it is an obviously honitsu-type riichi, it is not realistic.
The truly important question is: is the opponent the dealer, or not?
The dealer is still a real threat because of the 1.5x scoring.
Also, a riichi after a concealed kan is easy to treat as a high-value hand.
Example 5
Some players still push recklessly into riichi hands like this.
But once you remember that there are two possible ura-dora indicators here, the potential loss from dealing in is enormous.
Unless your own hand is exceptionally strong, you should avoid the fight.
That said, in the end, the value of a riichi usually cannot be read accurately.
Even if the dora is visible on the table, red fives and ura-dora still make high values very common,
so value reading against riichi is not very reliable.
Open hands are where estimated value matters much more.
From the yaku and the number of dora being used, it is usually not that hard to figure out roughly how many points an open hand is worth.
Theory Summary
Open hands reveal their value more easily, so estimated point value is a good push/fold factor against them.
Against riichi, uncertainty is too high, so unless the situation is unusual, such as a kan being involved, it matters more whether the riichi is from the dealer or a non-dealer.
The Probability That Folding Will Succeed
This is a very important factor in push/fold decisions.
If you have no genbutsu at all and very few tiles that even seem likely to pass,
then the standard play is often to keep pushing straight ahead.
But once several safe tiles begin to form in your hand, the situation changes.
Example 6
Riichi 
Hand Pon Draw 
Dora 
With this hand, there is absolutely nothing wrong with fighting by cutting 
.
After all, you do not have a single safe tile.
But what if one turn later 
passes?
Riichi
Hand Pon Draw Dora
You cannot really say that is dramatically more dangerous than .
But is this not exactly the point where you should switch over to folding?
This was only a 1000-point hand to begin with, and not one you really wanted to force.
Now you have three safe tiles, and the odds of folding all the way to exhaustive draw have become much higher.
So backing off here is what I would call good push/fold judgment.
These five items are the most basic materials for push/fold decisions.
Of course, once you reach South round, the score situation also becomes important,
but that belongs to the more advanced applications of push/fold, so we will return to it later.
For now, the key point is to learn how to judge hands using these materials.
Original Japanese page: http://beginners.biz/osihiki/osihiki02.html