How do you flirt with a long-term boyfriend?

okay, so i've been dating a boy for a year and seven months today(: he always says that he tries to flirt with me, but i never catch it. and usually it's sort of like, we BOTH have to be flirting for eachother to catch on, ya know? so i'm curious to know how i can flirt with him, and him catch it, ya know? it's sorta like, we've been dating so long, that flirting was the first part of the relationship, as it always is, and now we're just like, well we know we love eachother, who needs to flirt?--that sort of, married type of mentality(: i've tried the whole, playing it cute, being bashful, stuff, ya know, the usual. so what do i do to make him catch on, that i haven't already done?