What it says on the tin. How do you figure out who is safe and who isn't, especially among people you are getting to know or only have a work relationship with? Just any old idea, if it's in your head, post it here!
Raise LGBT topics withers them. Cook's recent announcement yesterday is a good one. So many people can talk about Apple products, so raising the CEO's recently revealed status is an easy ice breaker. See how people react.
Listen carefully to them when they are talking. Are they very conservative, opinionated or judgemental? Do they use inflammatory words? Do they demonstrate prejudice in their words or actions?
For me personally? Not openly, one other person (not direct coworker) in the building has an HRC sticker.