How to Handle Dora (1)
Dora are valuable because simply holding them raises the value of your hand.
That is exactly why it is important to learn how to play without wasting them.
Example 1
Pon 
Tsumo Dora 
In a hand like this, if you casually cut 
just because it looks like an Iipeikou shape,
Pon Tsumo
then you can no longer use the dora.
If you cut 
instead,
you can still swap 
out for the dora later.
To avoid this kind of basic mistake, always keep in mind what you will do if you draw the dora.
Example 2
Chi 
Tsumo Dora
If you cut 
,
you lose your dora acceptance here as well.
Because the hand also still has a possible 345 Sanshoku,
you have to securely cut 
.
Example 3
Tsumo Dora
Now one of your pairs has become unnecessary,
so you can break either one.
But if you think about dora acceptance,
you should cut .
Tsumo
Then if you draw the dora,
you can switch the head by cutting 
.
Some people might think:
"Even if I cut , couldn't I just leave floating as it is?"
But leaving tiles around the dora suji floating is dangerous,
and if you later draw 
, 
, 
, or 
,
you will once again be forced to choose between keeping or throwing away the dora acceptance.
So that line is incorrect.
Example 4
Tsumo Dora
This is a one-shanten hand that is holding a safety tile.
I think the correct play is to keep
and discard the safety tile instead.
Locking the shape in too early with a hand like this is not good play.
If you draw the dora 
,
not only does the hand become more valuable,
your acceptance also doubles from 12 tiles to 24 tiles.
Of course, I understand the concern that later you may no longer be able to discard safely.
But this hand is not high-value to begin with, and once you fall behind it is hard to fight back anyway.
If someone else declares riichi first, you can just fold honestly.
Theory Summary
When you discard, count your dora acceptance as well.
Especially in hands that lack both value and acceptance, you should not throw dora acceptance away.
Original Japanese page: http://beginners.biz/dora/dora01.html