My knights face the center of the board. My opponent's knights look off the edge of the table with their backs to the center. It makes my knights stronger.
I had an opponent once, who had to have his knights directly facing my king, for the whole game. Literally, every time I moved my king or he moved his knight, he would j'adoube so that each knight was pointed directly at my king. Psychological warfare?
I point them facing directly forward.
Most players seem to do this. Though, as pointed out earlier, it might not be the optimal approach, as it makes the pieces' appearance on the board less distinct, and grasping them is a bit less comfortable as well.
facing the left, like a diagram
As the king, it serves nothing if my knights grovel and kiss my royal arse. I want every man in my army and the woman who serves me all focusing on the same thing: the enemy. The enemy is that way (points toward the opposite side of the board). Thus I play with my knights pointing straight across the field.
I orientate them towards me. But why do I do it? Because of 2 reasons: To show my oponent how creative I am and see the reaction of his face.
Turning them towards you facilitates feeding them some of the apple slices from the snack table. Your steeds will then perform better in the middlegame.
I tend to face all of my pieces onto my opponent's king, because it feels like there is alot of pressure onto the king.