h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Ask yourself the question before commencing: Do I want this person as a partner?
If the answer is no then you are flirting if you enter into banter with them.
If the answer is yes then there is more to play for and you are on the route to chatting up. Thsi is often when you get tongue tied etc. so it may be in your interest to convince yourself that you are flirting.
An example of flirtation: two people work together but have no significant relationship.
She: "That's a nice tie,"
He: "I'm glad you like it, I put it on especially for you."

Analysis: She makes a pleasant comment to a co-worker. He makes an untrue statement which makes her comment sound much more significant by hinting that he knows her taste and panders to it.

To the observer you don't know whether you are witnessing the beginning of a relationship or people playing word games with one another.

I've been told I'm something of a flirt, but there is no way I would ever consider acting on flirtations. Happily married for a decade, two great kids, etc, etc...

I dunno. Harmless flirting makes the day go by a bit faster I reckon.