The rook is a very powerful piece, especially if you know how to make the most of it. In this first example, the black rook is in the corner where it begins the game. To make the rook as good as possible, try to move it to an open file where the pawns can't block the rook from moving forward. Rooks are more powerful on open files because they can then control the middle and far reaches of the board.
If it's good to put one rook on an open file, it's even better to put both rooks on open files! From these squares, the rooks help to control the important center of the board.
In the final example, we have two rooks but only a single open file. We therefore start by moving one rook to the open file and then moving it forward to make room for the other rook to move behind it. This is called "doubling rooks."
Making the most of an active rook:
Once you control an open file with a rook, you can often use the rook to penetrate your opponent's position. In the following diagram, the position looks quite even, but it is white's move. White takes the opportunity first to move the rook to the open file. Black cannot safely counter by moving his rook to the same file because white would immediately capture it.
It is therefore not possible to challenge the white rook, which can show off its strength by moving to the seventh rank in order to attack the black pawns. Once there, the white rook attacks two pawns simultaneously. Try as he might, black can only defend one of them. In positions like this, we say that white has a good rook while black has a bad one. It sounds almost simplistic, but masters always try to make sure that their pieces are better than their opponent's pieces.
Back rank mates:
Here's our first checkmate! In the first example, black has no defense for his king along the back rank. White can move the rook forward all the way until it attacks the black king. Black cannot move his king, capture the rook, or place a piece between the king and the attacking rook. It's checkmate!
In the second example, white shows off the power of doubled rooks. Here, black has a rook defending the back rank, but white has TWO attackers. As we learned early in life, two is better than one. White therefore moves the first rook all the way until it attacks the king. Black must capture the first rook, but white delivers the checkmate with the second rook!
Working with active rooks
This position illustrates why it's so important to control an open file with your rooks. As you can see, the black rooks completely dominate the only open file on the board. In many positions, the powerful rooks will advance across the board to attack and then capture the opponent's pawns. Here, however, black has a much stronger plan.
Black to move and checkmate in three moves!
Rooks can dominate knights!
The following diagram shows one important reason why rooks are more valued than knights. In this position, the knight can move to 4 squares, all marked with an "X" Note that the rook is able to cover all of the knight's possible moves. In such a position, perhaps white could march his king (or another piece) to attack and win the knight!
When you play over master games, be sure to look for this pattern: a rook two squares diagonally from the enemy knight. You will see it often.