Thou shalt not trade down to a king-and-pawn ending unless you can safely bet your first-born child on the result. Andrew Soltis, Grandmaster Secrets - Endings
If master players do not castle early, there is usually a good reason. When lesser players don't castle, they are usually misjudging the position. Andrew Martin, ChessMoves magazine
As far as possible each move in the opening should carry with it one or more threats. If you do not threaten anything, you give entire liberty to your opponent not only in the development of his pieces but also in the choice of his threats. Eugene Znosoko-Borovsky, How To Play The Chess Openings
Counterplay is the No1 priority of defence - even at the expense of other values such as king safety, pawn-structure, material and development. Andrew Soltis, The Art Of Defence In Chess
In the majority of cases the bishops [ie two bishops against two knights] are a positive force; so much so that modern players freely give up pawns (and even the exchange) in order to unleash their power. John Watson, Secrets Of Modern Chess Strategy
The king is a fearsome fighting unit in the endgame, about equal to a rook, say. It must be used as actively as possible, always bearing in mind that it is an important piece and must be looked after with great care. Jon Speelman, Endgame Preparation
The exchange is usually sufficient to win [in an ending] when there are pawns on both wings, because the rook's ability to attack from long range proves superior to the offensive or defensive powers of a minor piece. Andrew Soltis, Turning Advantage Into Victory In Chess