After 1.e4 c5 2.Nf3 d6 almost everybody plays 3.d4. But isn't this a positional error? I am not joking. I like my centre pawns, and I like a d pawn better than a c pawn! Bent Larsen, How To Open A Chess Game
The general rule of thumb for the Dragon and Accelerated Dragon (as well as most other Sicilians!) is that an exchange of knights on c6 will usually help Black, because the recapture...bxc6 will strengthen his control over the centre and provide him with a half-open b file. Andrew Greet, Starting Out: The Accelerated Dragon
Try to avoid making passive moves just to defend weak pawns. Sometimes they cannot be avoided, but often the pawn can be sacrificed for activity. Richard Palliser, Starting Out: Sicilian Najdorf
The presence of a bishop on the long diagonal [a1-h8] and a knight on f5 is a clear warning that something unpleasant is about to happen on g7. David LeMoir, Essential Chess Sacrifices
Tactics don't always work. If your opponent starts some tactics, it is important not to accept his idea at face value, but to look at it sceptically to see if it might contain a flaw. John Nunn, Learn Chess Tactics
A sacrifice of material in order to achieve a superior pawn-structure is often a typical method for the side wishing to obtain a static advantage. Valeri Beim, Lessons In Chess Strategy