Count routes, not rows
A pawn two rows from the finish may still face a long detour. Before each turn, trace the shortest open route for both sides. Include potential jumps over the other pawn: visual distance can be misleading.
Exercise: estimate how many pawn moves each side needs to finish in a current position, then trace the squares to check. Recount whenever the routes change rather than relying on an earlier estimate.
A wall costs a turn too
Making your opponent take two extra steps sounds useful, but placing the wall uses your turn and may slow your own route. Compare the extra distance for both players before choosing.
As a hypothetical example, a wall adding three moves to your opponent’s route while leaving yours unchanged is usually worth examining more closely than one adding two moves to both routes. This is a first evaluation, not a winning formula: your opponent can answer with walls of their own.
Block where detours are limited
The square directly ahead of your opponent is not always the best place to block. Look for passages where several routes converge. Blocking there may force a long retreat; blocking an open area with many exits often changes little.
Before placing, trace a detour around both ends of the wall. An open passage near one end may let your opponent escape cheaply. Also check whether the detour creates an opportunity for them to jump over your pawn.
Keep options for the finish
Spending every wall early removes your ability to respond. Saving walls while missing a winning move is no better. Whenever your opponent approaches the finish line, check immediate winning moves before continuing a long-term plan.
Exercise: play an offline game and explain the purpose of every wall you place. Before confirming, compare placing a wall with moving your pawn from the same position.
Practise one goal per game
In one Master game, focus on finding the shortest route; in the next, practise saving walls for the finish. Explain why moving or placing a wall is better each turn.
Compare two options before confirming. Start a new game to encounter a different style of response.