At the risk of some criticism, I am not always respectful during the national anthem, especially at home games.
We take a lot of pride in our pre-game presentation at M&T Bank Stadium. For our preface to these and our pre-game player introductions, I usually go to the field or to the WBAL/98 Rock radio booth. There, I can sense how loud the crowd is and how up they are for that game. By the time I make it back to my seat in the press box, the anthem has started and often is half finished.
That means I'm walking while the anthem is being sung, and when I get to my seat, I place an earpiece in that monitors the telecast of the game to make sure it is working.