If there is a 'good forcing move' available, it is probably the best move on the board, or, at any rate, the only move likely to be better is another forcing move. Cecil Purdy, The Search For Chess Perfection
For the offer of a pawn (in the opening) there must be one of four reasons: a) secure a tangible advantage in development; b) deflect the enemy queen; c) prevent the enemy from castling, either permanently or for several moves; d) build up a strong attack. Reuben Fine, The Ideas Behind The Chess Openings
When faced with an unfamiliar opening, or even an unfamiliar move in an opening you know, your first reaction should be to take a deep breath and try to understand what your opponent is doing. John Watson, Mastering The Chess Openings - Volume 4
In Closed Sicilians, with White playing e4 and d3, the most desirable place for Black's dark-square bishop is the long a1-h8 diagonal, (where) it has great influence both on the centre and the queenside. John Emms, Starting Out: King's Indian Attack