Tile efficiency
Tile efficiency refers to the speed of hand development. Having better tile efficiency means that the hand is more likely to complete, and is thus faster on average.
Only one person can win per round, and a hand of any value can win. Therefore, learning how to optimize tile efficiency is important to improving at riichi mahjong. Sometimes, it may not be best to go for the maximum efficiency play (e.g. slowing the hand to go for a yaku), but strong players should know how to reach maximum tile efficiency
Tile categories
Tiles can be grouped into a few basic categories:
Isolated
Isolated tiles, also known as "lone" or "floating" tiles, are those with no neighbors. A tile is isolated when there is no tiles numerically or categorically adjacent. Therefore, they may not be used for tile calls.
These tiles are not very useful, so they are often discarded first. However, an isolated tile may be used to "upgrade" the hand. For example, an isolated 5 can be used to improve the hand's shape. An isolated dora can be used to increase the value of the hand. An isolated yakuhai can be paired and then pon'd.
Taatsu
Taatsu 「塔子」, or "joints"/"shapes", are two tiles that can create a sequence. These resemble the basic wait patterns:
| Type | Ryanmen | Kanchan | Penchan |
|---|---|---|---|
| Incomplete |   |
 |
|
| Complete | /  |
|
|
All else equal, a ryanmen is twice as good as the other joints, because they accept twice as many tiles. Kanchans can be upgraded to ryanmens (e.g. 24-pin, after drawing 5, turns into 45-pin).
Toitsu
Toitsu are pairs. Most hands need 1 pair to win. Pairs can be used to create triplets, though, so having multiple pairs can increase efficiency.
Complex joints
Complex joints are a joint made up of 3 tiles. When the joint is completed, two tiles are used in the group, and the third tile becomes isolated.
| Type | Ryanmen + Pair | Kanchan + Pair | Ryankan |
|---|---|---|---|
| Incomplete | |
|
|
| Complete | / / |
/ |
/
|
Yaku
When building hands, yaku are certainly considered as they are a criteria for valid hands as well as added value to the hand. So, almost always, players have yaku in mind.
In other cases, players may end up simply having tenpai in mind, especially as the hand nears the later discards. This is of particular concern for the current dealer, who may have an interest in retaining the position and repeat the hand.
Counting tiles
When developing the hand, tiles take on different shapes, especially when taatsu are involved. The hand will lean in search of particular tiles, by which some many no longer be available. They may either be discarded, have one as the dora indicator, or be in a player's tile call. Any tile, whose whereabouts are unknown, are considered to be live tiles.