One golden rule for yours truly is - turn off the phone during the entire performance. I think people will understand why.
Which reminds me of the hoary old tale (paraphrased something like this):
Bloke goes into the toilet for a no.2. All at once a voice from the next cubicle calls out:
"Hello how are you?"
Bloke thinks for a bit, that's a bit odd, does he know me? Anyway he decides he'd better answer:
"I'm fine, thanks."
"What are you doing right now?"
"Going for a cr@p of course, same as you."
"Shall we meet up some time then?"
Whoa WHOA thinks the bloke - that's a bit fast! Sure it isn't someone I know, and anyway ....
"Just a minute, do I know you?"
"Ok then, in the pub, around seven..."
"Sorry, which pub?"
"Look, I'd better ring off and call you later. There's some prat in the next cubicle, keeps answering everything I say..."
