It is generally advantageous for your Pawns to occupy the middle of the
board, because when there they greatly retard the movements of the
opposing forces. The King's Pawn and Queen's Pawn, at their fourth
squares, are well posted, but it is not easy to maintain them in that
position, and if you are driven to advance one of them, the power of
both is much diminished. It is well, therefore, not to be too eager to
establish two Pawns abreast in the centre until you are fully able to
sustain them there.

When you have two Pawns abreast, the King and Queen's, for instance, at
their fourth squares, should the adversary attack one of them with a
Pawn, it is occasionally better to advance the Pawn that is attacked
another step, than to take the Pawn.

The Pawns, however, should seldom be far advanced, unless they can be
properly sustained by the Pieces. Pawns at their fourth squares are
therefore mostly more powerful than at their sixth.

The King's Bishop's Pawn having no support but that of the King, is
usually the point to which the first attack is directed, and more than
ordinary care should be taken to preserve it. It is rarely good play to
move the King's Bishop's Pawn to Bishop's 3d early in the game.

As a general rule, it is not advisable to move King's Knight's Pawn or
Queen's Knight's Pawn early in the game. The former played to K. Kt's 3d
square will often allow your adversary to play his Queen's Bishop to
your King's Rook's 3d square, a dangerous move when you have castled on
King's side.