[DampRobot]

Because everyone else has posted such great stuff, I'll keep my comments brief. This experience comes first hand, as well as from listening to many of "the greats".

You should work closely with your scouts, before and after matches. You should never go into a match not having a good idea of who you're competing with and who you'll be facing.

Don't get tunnel vision to your team. Especially if your drivers know what your role is in a match, you can sometimes make far more difference coaching annother mediocre robot to great defense than by telling your team what they already know to do. This is even more true in elims, when how a third seed plays will often make or break an alliance.

Finally, and most importantly, your job as coach is to tell your drivers how much more time they have and what the score is. They don't have time to look at the scoreboard in a match, and them having this information is critical. More so than anything else, this is your job as soon as the match begins.

To review:
1) Know thine enemy (and alliance partners).
2) Work with other teams during the match, if appropriate.
3) Never leave your alliance partners guessing about time or score.