Palms Up Thumbs Down
Catchers, there is no quicker way to lose a strike call than to receive a pitch with palm of your mitt facing up.
It doesn't matter how great the pitch was, it is an automatic "BALL!" from the umpire.
With proper receiving mechanics, the palm of the mitt will face in towards the plate (pitches on the corners) and down towards the ground (pitches down the middle), but it should never face up.
Think of the strike zone through the eyes of the umpire behind you - How you present those pitches to the umpire will affect their ability to make the correct call. If you go "Palm Up" you're going to get a big "Thumbs Down" from the umpire.