You give a coach a T and...

[refnrev]

I've never had a coach whom I T'd up who didn't know exactly what they did and why they got it. I've never needed to explain it. If I give one to a player, that's different. I explain what they did and why it was a T. Never had a problem with it because all were clearly deserved. One thing though, is not to make a big dramatic production of it. Don't hold the T for a long time, act like you're breaking your fingers you hit it so hard, etc. Give it dispassionately, report it, and get on with the game.