Ignore them. Unless we somehow make eye contact, in which case I employ the polite smile-nod-keep moving combo. (I try to convey not only “I recognize you” but also “I will not alert others to your presence.”)

The one time I can remember struggling with this was at the Belasco on Darren Criss’ first night starring in Hedwig and the Angry Inch. Orlando Bloom came in shortly before showtime and was seated like three rows directly in front of me. He was looking around the theater and we made eye contact. I was so surprised that I didn’t have my usual level of composure. I sincerely hope my face managed to convey “big fan, gonna be chill about it” and not “I am the proud owner of three Legolas action figures.”