Oh Lord, I've only really learned how/learned to enjoy flirting since I got married. I think it's the safety thing: I can flirt now because there's no pressure, no expectation, no real desire for anything to come of it.
The biggest act of flirtation I ever did, really, was to drink beer. (I generally hate beer.) My husband and I met at a wedding. The keg from the reception ended up at his house, and at the wedding he invited me to brunch at his house the next day, to eat leftovers and drink of the keg while it was still drinkable. A beer bruch. I didn't have the presence of mind to say "I don't like beer, but I like you!" So I just came and drank beer. And came back that night and drank more, and then came back again on Tuesday, and then it was gone (whew). It was secret flirting. I guess it doesn't count as flirting but rather as just one of those things you have to do. Also, I remember positioning myself near him when we were looking at wedding pictures on the tv screen. Much later, he said he was able to smell my perfume when I was standing there. Very subtle but it seems to have worked alright.