Getting killed by Knights

I seem to be clueless and defenseless against my opponents knights.  I assume this probably means I don't use them well, either.  Can someone point me in the right direction for tactics training/videos/etc?  Thanks!

To play against knights, take away their advanced support points. -Steinitz

What do you mean with advanced support points -- advanced pawns?

Support points are square that the Knights can use as home. Using pawns to take away their post/square is one way to get them out of good squares.

Exchange your Bishops against them first chance you get

This leaves him with two knights versus a bishop pair.  As the game goes on and the board clears up, bishops begin to overtake knights in strength, and one of the things postulated by the OP is that he's not using his knights to their fullest.