I think If I had an opponent place his knights facing backwards, I would have to adjust them when it was my move.
How do you place your knights on the chess board?

The heads of my knights always face horizontally...(like towards each other)..kinda like Magnus Carlsen! :D

depends on the situation of the board. I point my Knight where I will have a challenge, just to remind me that I should do something about that sooner or later!

I point mine inwards at the beginning. When I move them I usually keep them the way they were when I picked them up, so as White my QN will be facing right, KN will be facing left, etc.
I usually don't pay attention to them, but they frequently end up backwards just because I sometimes grab them by the nose. If that seems to upset my opponent (and I know him somewhat), I'll start turning them in wierd directions on purpose (and I'll sometimes even adjust his to be backwards).

In the begining: I try to position mine so that they, and I, appear to be staring down my opponent.
During the game: I point it toward where my opponent thinks it is going. (And away from where it really is going.)

I face mine toward the center of the board actually.
An old college pal of mine had a great story about how he was playing this guy who would adjust my friend's knight after a move. After a couple moves, he figured that this bugged him, so he tried to move his Knights as much as possible to intentionally face them backwards or sideways just to irritate him. Eventually the poor nut just snapped and made a horrible error & lost.
Do you know how you place your knights on the chessboard?
By this I mean, where do the horse heads point?
I place mine, facing forward, ready to do battle!
Seems most have the head facing left or right, as in a chess diagram.
I only ran into one player who pointed them backwards.