Most of the things I was going to add have been summed up by Andy, Amy and Karthik.
I have had had the fortunate experience of being a FIRST driver for 3 years, and now a field coach. The mentor on our team that was my coach jokes that I was groomed to be a coach, but I kind of was.
Personally I think the greatest thing a coach can do is be very close to the drive team. I try and always be around them, in the pits, sitting in the stand watching matches, driving in the vans. I am my drive team's stalker. Having a good relationship with them enables so many things.
Also as a coach and as others have said, you can't take crap from anyone. You have to be able to hold your own and keep everything away from your drivers, let them do their thing.
I cannot stress enough the importance of pre-match strategy sessions. Make it happen.
That's about all I can say for now, listen to the others
Ricky Q.
driver in 100+ matches, up and coming field coach