My son tried-out as a ctacher at the start of his freshman year....he is going to be a junior. Basically played infield and pitched in little league and juniors.
I guess the most important things are learning the correct way to 'block' pitches, and when. Then you need to have quick feet and a quick release for runners trying to steal. I would then say that your squatting setup should be 'still' and you need to learn how to "frame" pitches. Calling pitches, if your coaches don't do that, are important as well.
You need to have your pitcher feel comfortable in knowing that you are capable of handling whatever he throws your way. Pitchers have huge egos and you need to try and understand that if things aren't going their way, you have to be very supportive, and calming, so they can relax and stay focused during the game. This is where leadership comes into play.
You have a tremendous responsibility to your pitcher and your team. A simple missed 'block' (passed ball) can make the difference between a win and a loss. Sure other players can make errors, but you have to think about the fact that a catcher throws more during the game than any other psoition player, including your pitcher.
You can get fatigued, get turned in the wrong direction on a pop-up, over throw a runner trying to steal, or under throw, or even forget how many outs there are (my son caught his third game freshman year and his team was getting beat-up, a lot of hits, errors, you know quick "bang-bang" type of situations. Gave the opposition 4 outs!!! Players didn't know, umpires didn't say anything, coaches didn't say anything, but man, when he got into the dugout, guess who heard about it? The catcher, the leader. He'll never do that again!!!!).
Anyway......go and do a "search" in your 'browser' and look-up websites that are specific for catchers, there are plenty. Another great source of information about this is a webster known as "Fungo". His son will be a junior at Auburn University and is their catcher. I contacted him when my son started. He is a fantastic person who shared information and experiences with our family. Private message him, and if you do, tell him Boomer said hi!!!!
Work hard, and best of luck to you!!
BoomerIL