As mentioned before, unless you're aiming for a chitoitsu, you shouldn't have too many toitsu in your hand. Normally, the limit would be 2 toitsu, any more will result in a bad shape. If you find that there are too many toitsu in your hand, there a few options.
a) Dismantle and discard
b) Combine the toitsu with the other tiles in your hand to form a good shape
c) Make a chitoitsu
Beginners are often reluctant to discard redundant toitsu, for example
|(sha as guest wind)|
Actually when it comes to effective tile loss, the loss of discarding 3 pin will only be the other two 3 pin. However if you discard 3 sou, the loss will be 124 sou, a total of 12 tiles. In a situation with a lack of mentsu, relying on the toitsu in your hand to complete your hand will often result in failure.
When you have 2-3 toitsu in your hand, and if deciding on a jantou is too early, you can consider discarding a toitsu, leave a useful isolated tile, yakuhai etc, and increase the chances of getting a good shape or forming of mentsu as much as possible... This is not only a method of playing that beginners neglect, even for an intermediate mahjong player, this is a blind spot that is often missed.
For those hands with 4 toitsu and above, normally you can view chitoitsu as a possible choice.
This is the game record of MFC, at that time I was the north player. At the fourth draw, I drew 9 sou. What should I do?
If you consider a mentsu hand's(4 mentsu + 1 jantou) tile efficiency, discarding 9 sou here is normal.
On the surface you can easily make mentsu hand with so many toitsu, but it's the opposite. Currently there is only one confirmed mentsu of 789. The rest of the tiles: 4 wan, 9 wan, 3 pin and sha require drawing two more tiles to win. Every type of tile only has two more tiles, the efficiency is really low. The most important thing is, for the toitsu here to have a good evolution, it's not an easy feat.
Therefore this hand should aim for a chitoitsu. I discarded 2 sou in the actual game.
PS: Tile efficiency is a huge learning ground, there are many more things to explain. But in order for the readers to learn other more important theories, I will first set aside theories regarding tile efficiency. Once other parts have been discussed, I will write more articles on tile efficiency.