Here's a tip to celebrities performing this year: There's a dress code on the biggest night of the year. Look to those who came before you and follow their lead.
2012, Lady Gaga

Sparkly catsuits = always in style.
Image by Jemal Countess / Getty Images
2012, Lady Gaga, again.

Looking like the Statue of Liberty = also always in style.
Image by Jemal Countess / Getty Images
2012, Florence Welch

Flowing robes, naturally, for Florence.
Image by Kevin Winter / Getty Images
2011, Natasha Bedingfield

Grandma-chic.
Image by Natasha Bedingfield / Getty Images