Working rec games has helped me quite a bit. However, there are some dangers. The first is developing, or devolving to, "rec league mechanics." You have to rage against that. Second is developing a cynical attitude about all ball players and coaches. That can hurt you if you take it into a HS game. Third is staying too long. There comes a time in every official's career where rec league isn't going to help him/her any more. At that point, it's time to leave it for the new guys.
Oh, I forgot one. It's important to remember to switch hands for every T. Otherwise you stand a real chance of developing a RSI.
