[oison75]

Well, first off, yelling probably isn't the best. During comps everyone's on edge and the last thing other people want is to be yelled at by an emotional teenager. Believe me, I've been there.
From experience, I've found the best possible thing you can do is to speak calmly and concisely. People usually prefer getting information in the easiest way possible, without feeling distrespected.
I know that being calm during comps is REALLY hard, but try to make an effort to at least "appear" calm and collected; people will respect you more (and listen to you!).
During a match, if you need to talk to another teams coach, walk away from your driver station, trust that your driver will take care of things while you're gone, and just talk to them (usually it ends up being short mumbles like "get them- we're down" or "get them off us").
Remember to be watching the whole field, and not just your robot; this is the point of having a coach.
Hope that helps