Minecraft wiki entry for Ladder, associated text: It is possible to use ladders one block apart in a corner by placing every other ladder on the alternating side of the corner. This method requires jumping and shifting sides constantly.
By holding the jump key, players can still use water ladders that have ladders placed every other block.
If the player stops on a ladder and places a sign, the player remains in midair without having to hold Shift, because the game is paused in singleplayer.‌[Java Edition only] This does not work in multiplayer because the game is not paused.
Attempting to place a ladder on a spot another ladder occupies may instead place the ladder somewhere nearby (because of the ladder's hitbox).
It is possible to remove a ladder while standing on a ladder and holding the sneak key, but it can take a long time because the countdown for breaking the ladder often resets.
In Java Edition, sticks can be crafted into ladders to gain a slight bonus in fuel efficiency. While 7 sticks can smelt 3.5 items, if they are crafted into 3 ladders, 4.5 items can be smelted.