Flushes (1)
Flush hands, especially Honitsu, are extremely important yaku.
They are worth 3 han closed and still 2 han after calling, yet they are not hard to build.
Very few yaku are treated this generously in terms of score.
They do have the drawback of being easy to read, but they are still something you should aim at aggressively.
If your hand has the right material, this is one of the few yaku you may legitimately decide to pursue from the initial deal.
This page looks at when you should aim for a flush based on your hand alone.
Besides your hand itself, there are three other factors that matter:
- table situation
- turn count
- score situation
But on this page, we assume an early East-round flat game with little score movement,
and judge only from the hand itself.
Example 1
Tsumo 
Dora 
There are 11 souzu here, and the shape is excellent.
The terminal is paired, and the tiles connect all the way from through .
This is practically a hand shouting, “Please play Chinitsu.”
Unless it is already very late in the hand, you should head for Chinitsu.
Thinking about future danger, start by cutting .
Normally, you would begin with so that a future 
draw keeps a manzu ryanmen improvement.
But in a shape this strong, you do not even need that manzu ryanmen change.
Example 2
Tsumo 
Dora
But having 10 tiles in one suit does not automatically mean you should always go for a flush.
Example 2 has 10 pinzu,
but you should still simply discard .
This hand is naturally a Pinfu-Riichi hand,
and depending on the draw it can also pick up Tanyao, Sanshoku, or Ittsuu.
There is no need to force a flush on a hand that is already plenty good without one.
“It looks like it might become a flush, so I’ll go for it.”
Playing with that kind of instinct is dangerous.
Forcing a flush by breaking an already completed meld is basically wrong.
Theory Summary
Do not force a flush on a hand that does not need one.
Dropping a full meld is basically forbidden.
Example 3
Tsumo Dora
But mahjong always has exceptions.
In a hand like Example 3, if going for the flush raises the value dramatically,
and the resulting shape is still easy to win with, then it is fine to break the pinzu meld and commit.
Still, this is one of the rare exceptions.
In a flat game, there are very few hands where dropping a whole meld just to force a flush is correct.
Example 4
Tsumo Dora
If you have two pairs of value honors, you should lean toward one suit and aim for mangan.
In Example 4, even though there is a dora-containing taatsu, you should of course aim for a souzu Honitsu.
But there is an important caution here.
Many beginners immediately start by discarding the dora ,
which is overdoing it.
The weakness of Honitsu is that it is easy to read.
If you start peeling the kanchan shape from the dora,
the rest of the table can almost confirm that you are on a souzu Honitsu, so naturally they will defend harder.
Since you already have such a strong hand,
you should normally start with and keep your discards unobtrusive, making the hand at least a little easier to win with.
Even if the flush is the main line, you could still immediately draw afterward.
Theory Summary
If you have two pairs of value honors,
try to combine them with a flush and aim for mangan.
Example 5
Tsumo Dora
Assume is just a guest wind.
To be blunt, this is garbage, but if it were me, I would start by cutting something like and aim for a souzu Honitsu.
If you just play the hand naturally, you probably are not winning anyway.
This is a very distant Honitsu attempt.
If you are likely to switch into defense later,
then it can actually be reasonable to start by cutting middle tiles, making the table more cautious while strengthening your own defensive structure.
In terms of bluff effect, calling would naturally attract more attention;
but from a defensive point of view, this is a hand you should not call with.
If your opponents' hands are average or better, they can still just advance normally.
In mahjong, bluffing itself is not all that powerful.
Unless or pairs up, I think the better plan is not to push for a win.
Beginners would often pon the very first ,
but this is exactly the kind of hand where you need to realize that it is not really a hand you can win easily with.
“It is fine not to win with this hand.”
That kind of composure matters.
Theory Summary
When aiming at a distant, difficult Honitsu, prioritize defense.
Do not force calls before the hand actually starts to look winnable.
Original Japanese page: http://beginners.biz/teyaku/teyaku06.html