Coached one tonight and honestly i had good time. My set of newbies must have been a good batch because they all listened to me pretty well. One piece of advice I can give to coaches it to explain why you're saying to do something. Yeah it's hard to give a good explanation during a game but c'mon this isn't lan finals. Miss a few comms to tell them WHY you want to force uber and get out without losing any players or whatever. If you have a scout who does nothing but +forward during holds call him out. If he's there to improve he should be accepting of criticism, and if not he shouldn't be there at all. Don't be a dick about it but make sure they know what they're doing isn't good play.
My advice to newbies is not to be afraid to ask questions. The reason I'm coaching is to be helpful and if I spend 25 minutes trying to teach and then everybody just leaves right after the game I won't feel like anything rubbed off. When you ask something it makes me feel accomplished :). That's the feeling that will keep coaches coming back. If they feel like their time is being wasted they won't want to do it anymore.