What to wear: A white wig pulled halfway up, a long white or blue dress, and some fierce jewelry made of horns or steel. You can also be Vaes Dothrak Dany, which would require either wearing a dirty brown sack dress or wearing a nude bodysuit and pinning a bunch of flames to it. Bonus points if you can find some toy dragons.
How to act: Quietly confident, but assert your status as the Mother of Dragons if provoked. Ask everyone where . . . your . . . dragons . . . are.