I agree with winkydink - the quicker the pace the better. A good catcher can whip that ball back to you with you already on the rubber, and a quick pace (changed up sometimes) keeps the ump happy and the players behind you alert.
HOWEVER, many leagues have a rule where the pitcher must "present" the ball before pitching. In other words, you have to be stationary on the rubber, and hold the ball in front of you before you pitch.
I pitched in recreational leagues till I was 49 years old. My second to last game, I got my nose broke on a one bouncer. (I saw it all the way, but the ball made it to my nose before my hands got in position to catch). My glasses went flying, but I got the guy out at first - he was standing there wondering if I was all right.
My last game, I broke my finger covering home (the worst female player on co-ed teams always plays catcher) on a throw from the outfield.
The reflexes aren't there anymore, so I am now retired.
One other tip - a strong cross wind can carry a slow pitch a good foot or two, so sometimes you'll be aiming right at the batter or a foot or more outside and watch that ball float over the plate.