From a Marine Corps Colonel in Afghanistan:

With all the kindness I can muster, I give this one piece of advice
to the next pop star who is asked to sing the national anthem at a sporting event...
Save the vocal gymnastics and the physical gyrations for your concerts.
Just sing this song the way you were taught to sing it in kindergarten -straight up, no styling.
Sing it with the constant awareness that there are soldiers, sailors,
airmen and Marines watching you from bases and outposts all over the
world. Don't make them cringe with your self-centered ego gratification.
Sing it as if you are standing before a row of 86-year-old WWII vets
wearing their Purple Hearts, Silver Stars and flag pins on their
cardigans and you want them to be proud of you for honoring them and
the country they love - not because you want them to think you are a
superstar musician. They could see that from your costume, makeup and your entourage.
Sing 'The Star Spangled Banner' with the courtesy and humility that tells the audience that it is about America, not you.
Francis Scott Key does not need any help ."