Statistics culled from numerous tournaments reveal that rook endings comprise 50% of all endgames, and it is for this reason that a study of them is of great practical value. Grigory Levenfish & Vasily Smyslov, Rook Endings
Learn to use a chess program, eg ChessBase, in order to improve speed and efficiency (when studying the opening), and to make study more fun. Andreas Tzermiadianos, How To Beat The French Defence
At master level (approximately 2360 elo) and above, a pawn deficit is generally decisive. From there down to 1800 elo a pawn deficit on its own need not be disastrous, unless the inferior side cannot avoid a simple losing endgame. Below that level, a two-pawn deficit (or a piece for a pawn or two) can often be overcome. David LeMoir, How To Be Lucky In Chess
If your opponent ends up with an isolated pawn, make sure you control the square directly in front of it. Aside from stopping the pawn in its tracks, the square will turn our to be an excellent home (support point) for one of your pieces. Jeremy Silman, The Reassess Your Chess Workbook
The command of an open file by a rook, or by both rooks, represents a great advantage, particularly if the file is the only one open, and the opponent cannot reply by occupying it with a rook. Siegbert Tarrasch, The Game Of Chess