The biggest advantage in sticking to respectable main lines is that you can rest assured that the opening you are playing is fundamentally sound, and is not likely ever to be refuted. Steve Giddins, How To Build Your Chess Opening Repertoire
In order to handle pawns well, it is important to learn not to handle them too much. Preparing is better than repairing. Savielly Tartakower, A Breviary Of Chess
Always be wary of old theory in very sharp positions. There may well be a dangerous improvement lurking which computers will quickly spot. Richard Palliser, Starting Out: Sicilian Najdorf
It is not sufficient to be a master of one opening. You must also be a jack of all the rest! Sure, go ahead and learn one defence thoroughly, but also get a feel for the others. Force yourself to play through master games or play some blitz games. You only require some general knowledge of the general principles. John Emms, Chess For The Rank And File
When your intuition tells you that there should be a forcing combination in the position, but your concrete analysis can't make it work, try the brainstorming technique of reversing the move-order. Lev Alburt, Chess Rules Of Thumb
The creation of an operation base for the knight is one of the most important motifs in chess strategy. Luděk Pachman, Complete Chess Strategy 1: Planning The Pieces