One good way to exploit a strong central advantage is to use the extra space [it gives] your pieces to launch a flank attack. Richard Palliser, Starting Out: Closed Sicilian
Activity is vital in endgames. If you are defending, don't defend absolutely passively unless either the draw is cast-iron or you are absolutely forced to. Jon Speelman, Endgame Preparation
If you face a choice between equally good continuations, there is no need to contemplate for long. Quite the opposite: you can choose one without making a big mistake. Ján Markoš, The Secret Ingredient To Winning At Chess
Chess patterns will often repeat themselves according to the opening that was employed, which is why playing through complete games with a particular opening will help someone play that opening well. Nigel Davies, The Rules Of Winning Chess
Whether you are a new advocate or a seasoned exponent of the English, you will inevitably enhance your understanding by studying complete games, which demonstrate how ideas in the opening are continued into the middlegame and endgame. Nigel Povah, How To Play The English Opening
It's better not to change entire lines or systems, but to tinker a bit so as to make one less predictable, while retaining the knowledge of the ideas behind the lines. Junior Tay, Chess magazine