After a few rounds of discards, you'd normally be able to get rid of any useless honour tiles. If the remaining tiles do not form mentsu, you can roughly separate them into three types.
2. Isolated tiles (Number tiles that are alone)
The next few paragraphs will first explain the taatsu problem.
The types of taatsu
Taatsu can be separated into ryanmen, kanchan and penchan. The value of penchan is the lowest, followed by kanchan, while ryanmen holds the highest value. Therefore when you have too many taatsu and need to break up one, start with the one with the lowest value.
You should discard 12 wan here.
If you need to choose between discarding taatsu of the same type, you can consider which one of the two will be able to evolve into a better shape.
In this kind of situation, there are two ways of breaking down the taatsu: 24 wan and 35 pin. On the surface, 24 and 35 are the same, but there are differences. You can form ryanmen with 35 pin by drawing 2 or 6 pin. However with 24 wan, drawing 1 wan will turn it into a penchan. Therefore the probability with 24 wan is lower than 35 pin. To preserve the possibility of drawing 5 wan, discard 2 wan first.
Therefore beginners should memorize this order of values
Penchan < 13 Kanchan < 24 kanchan < 35 kanchan << Other middle kanchan <<< Ryanmen