The Basics of Red-Five Mahjong
Nowadays, most mahjong parlors use red fives.
Especially in free-play parlors, some places even attach chip bonuses to them or allow hands that win on red tiles alone.
Now that red-five mahjong is the mainstream, you need a style of play that matches it.
Prioritize Hand Width Over Yaku
Because there are so many bonus tiles, you can still win a big hand even without forcing yaku.
Do not get too hung up on yaku. Focus on hand width and speed.
Example 1
Tsumo 
Dora
At first glance this looks like a guaranteed Sanshoku hand,
but breaking away from the pinzu kanchan is faster.
It feels awkward to destroy a nice Sanshoku line, but this is exactly how red-five mahjong should be played.
Do Not Obsess Over Staying Menzen
If you already have plenty of dora, even an open hand can still bring in a decent score.
Calling is an extremely important skill in red-five mahjong.
Example 2
Opening for Tanyao and a 3900 hand looks easier to win.
You can pon , and chi on , , , , or 
. Any of them is fine.
Even calls that do not reduce shanten are used routinely in red-five mahjong.
Chanta-Type Hands Are Unfavorable
Try not to aim for Chanta, Junchan, or Honroutou, because those hands cannot use red fives.
The usual ending is that someone else calls a red-related tile and wins, almost as if they were saying, “Thanks for the meal.”
Even if no one calls, you still have to discard dangerous 4, 5, and 6 tiles late in the hand, which is unpleasant.
In red-five mahjong, 4 through 6 are dangerous in the first place.
If you hold , of course you will accept the kanchan on .
And once someone holds a red tile, everyone starts looking for shapes that connect to that red,
so 3-6 and 4-7 suji become quite dangerous.
Also, 5 tiles become waiting tiles more often than usual, and even red-tile tanki waits exist.
That is why aiming for Chanta-type hands is usually not profitable.
Example 3
Dora
Of course, if the hand is already shaped this well, you still go for it.
But if you call and win for 1000 or 2000, just take the quick win.
Many strategy books say, “Do not make cheap open Chanta hands,” but that idea is outdated.
Rather than sitting back and insisting on a closed hand, I think you should use the advantage that the hand is easier to call.
It would be dull to sit there carefully building a closed hand only to end up watching someone else tsumo Menpin Red Red, right?
Think About Red-Tile Acceptance
Just like with normal dora, try to build your hand into shapes where drawing a red tile will not cause trouble.
Tsumo
At one-shanten, should you cut or ?
Normally, people say cutting is correct.
Why? Because suppose someone declares riichi later.
If you then draw again,
you can at least discard the somewhat safer instead of the more dangerous .
But in red-five mahjong, you should definitely cut .
Because if you draw , you can swap it in for .
Original Japanese page: http://beginners.biz/dora/dora06.html