I love threads like this. I started keeping when I was about 21, playing for my club's 5th XI, and by the time I was 26 I was being called into the 1sts. I'm not first choice but certainly a capable deputy, I've even taken leg side stumpings stood up to an ex-County seamer!
Anyway, the key is practice and mindset. Once I got the bug I just wanted to be the best I could, which meant setting myself challenges and practicing the skills I wasn't so good at. First it was aiming for no byes conceded, then I worked my way up to being a reliable catcher and then a more attacking keeper who could help to create chances either by standing up to quicks or by taking sharp stumpings.
I'm also tall with bad knees, so I find the Z position most efficient. I lead with my head and focus on moving with the ball, which helps me get into line early. I also try to keep my hands within my peripheral vision (ie not on the floor when I crouch) so that I can always see both hands and ball. Basically do everything I can do get in the right position to take the ball and more often than not my hands will be in the right place.
Smaller keepers will always have the advantage of movement but they're also less likely to take that spectacular full length diving catch ;-)
Also, don't be too proud to wear a helmet if it helps you keep your eyes on the ball.