Place your rook BEHIND a passed pawn if the pawn has crossed the middle line.
The King is a champion pawn-blockader. Therefore, prefer to have passed pawns on the side where the enemy King does not stand.
Rook on the seventh rank is particularly deadly if the enemy King is confined to the eighth rank.
In rook endings, strive to decrease the mobility of the enemy rook or rooks and to increase the mobility of your own.
Whether an advanced pawn is yours or the opponent's, our rook is best placed behind it.