Just generally try not to offend people so instead of saying "that's gay!" or "how gay" I would replace the word with annoying, stupid, weird or a made up word.
I never call people gay, Idk it doesnt seem right. What if they are? It's as if you're saying they're a crime against humanity for being "gay", and they actually are gay so they're proving your point.
I haven't heard it recently though, surprisingly, so I don't think about it. I do think that it offends boys much more than girls though for the simple reason that being "gay" leaves that stereotype on them that they may dislike because loads of 12 year olds try their best to act as macho as possible. *is not ageist*