I think it's mostly in the attitude. I can't really define flirting, but I always think one component is just hints of sexuality coming into play. You wouldn't say 'I had sex the other day' or anything like that, but if she's describing something that she did on the beach, you might say 'mmmmmm, you on the beach: I'd like to see that.'
It's fun and suggestive, and I suppose, a little romantic. I'm not that good at it, but that's what I think it is...
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My type of joke... 'Three guys walk into a bar. One of them is a wee bit stupid, and the whole scene unfolds with a tedious inevitibility.'
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