What do you do when someone you are with starts talking about something you have no interest in?

It depends on who it is that is boring me and what the topic is.
 
Sometimes I find something to laugh at and have them start laughing at something entirely different.
 This also falls under changing the topic, not-so-gracefully.
Sometimes I cry.
Sometimes I urgently have to pee.
Sometimes I fake sneeze and say my allergies are acting up.
Sometimes I ask them an off-the-wall subject.
Sometimes I stare at them with that blank stare.  Rarely though.  This one is rather rude.
Sometimes I cry.  I can't do this on command.  I have to really go somewhere deep and sad.  It's another tough one.
Sometimes I ask them to start analyzing  why they are so interested in this subject.  I might find an incling that would interest me.
Sometimes I am polite and wait it through.
Sometimes I just nod and smile.
Sometimes I think of all the ways I can get them off the subject, gracefully.
That is all I can think of that I've done at the moment.