I try not to... I sometimes do it online (if I can't resist the humor) but it seems corny. I'm trying to avoid it, actually. Even online.
I sometimes flirt, but I'm more interested in having a good laugh. Flirting is fun, but I love to laugh and joke and tease in a humorous way. If I do flirt, I have motives!
I made two comments to my wife to be when we were getting to know each other. Probably fall into sexual harassment. I don't know why I made either comment, but I got busted / embarrassed both times. They just confirmed that I wasn't meant to be a flirt. First one, we worked together in a small room in a records department of a Probation Department. She took documents in through a window at the end of the room so I had plenty of time to watch her tush. I got up some courage, went over to her at the window and told her I had an urge to pat her fanny. Meaning tush. She looked at me with a VERY surprised expression and explained that in Australia "fanny" means "lady parts". (She's Australian.) I had just told her I wanted to grope her crotch... I went red and crawled back to my desk while she had a laugh. Another time we were talking on the phone and I told her I was going to get an "all over" sun tan and come to her apartment to show it to her. This was pretty audacious stuff for me and I don't know what got me there. I expected some sort of comment, but she just said, "OK,". There was no way in hell I'd pull something like that so that fell flat. Actually, I did spend time at the beach in a Speedo. I always tan quickly and well. Sometime later we became an item and she took a Poloroid photo of me walking around her apartment fully aroused after we'd had a romp in bed one day. Speedo tan line included.