Haha I feel you on that. I would never catcall a woman but I have to admit, if I was walking down the street and some lady looked at me and made a comment about my ass or something it would make me smile. I try to be unaggressive and approach it more like a conversation than flirting at first. Some people like to be flirted with a bit more directly but it's better to start more casually in case they don't.