Tips and tricks
Suppose we have this situation. There are two linked ladders here
How to block properly (by lazyplayer)
If your blocking move has too little influence on both your edges, then the opponent has at least two good zones of the board that are worth trying, one for each side. For example, compare the situation for blue in these two cases.
In this case, the blue initial pieces (E9 and F7) have very little influence on both blue's edges and thus don't provide any immediate threat on bottom. Blue has no choice but to play D8, which however is still far from being connected to any blue's edge.
This position on the other hand is quite more tricky for red to play correctly than the first. Blue is still too much focused (unavoidably, given the weak position) on bottom but, after having obtained a reasonable influence on the right side, he can now concentrate his efforts on the left side of the board.