Every couple needs to set some ground rules, especially for areas where emotions run high. (If the word rules itself makes you balk, consider that a culture is defined by its implicit rules of conduct, so what I’m really talking about is the mini-culture of your romance.) You probably don’t have to formally discuss whether it is the pants-wearer’s or the laundry-doer’s responsibility to check pockets for cash (although it probably wouldn’t hurt), but you’d better nail down what’s acceptable and what’s not when it comes to flirting.
I’ve met couples with rules so strict they would shock a Puritan: No talking to members of the opposite sex outside of work, and only bare minimum contact at the office. I’ve also met couples with no holds barred, with little more restriction on sexual behavior than they'd when they were single. Neither extreme is sustainable for most couples.
Before settling on your own rules, ask yourselves these questions:
Many couples feel comfortable drawing a line at flirting that leads to physical contact, but are then surprised and disturbed to find how much fully virtual online relationships (or phone sex) feel like a betrayal, especially when they involve acknowledgements of mutual attraction. Others draw the line at any sexualized behavior, and then find that a source of pleasure and self-esteem in their lives has been lost.
I’ve suggested to many couples a rule that you can do whatever you feel like as long as no one can tell that it’s sexual, including the person you’re doing it with. This rule allows for some pleasure when you, apparently innocently, get other people to flirt with you, but it also protects your partner’s face (as long as you don’t get caught) and potential for hurt feelings (as long as you follow the rule).
But that’s just one idea. You can develop your own guidelines for flirting after discussing the questions I’ve listed.