Developing the Knights is often a no-brainer in the opening. The White Knights are posted best on f3 and c3, where they attack two center squares; ditto for the Black Knights on f6 and c6.
The next best squares are e2 and d2, where they attack one center square. The downside of these posts is that they interfere with the movement of the Bishops. The Knights can swap places by playing Nb1-d2-f3 and Ng1-e2-c3, but this loses a move each compared with the more direct Nb1-c3 and Ng1-f3.
The worst posts for the Knights are on h3 and a3, where they have no influence on the center. These squares are only justified when the plan is to continue to another square : Nb1-a3-c4 (or -c2 or -b5).
