Metro - Looking for expert advice on science of flirting

The Metro is writing a light-hearted feature on the science of flirting:
They are keen to hear from experts regarding:
*what is/isn't flirting
*what's happening physically and mentally (flirting is known to boost your self-esteem, reduce stress and improves your communication skills etc)
*what makes a good (and bad) flirt
*why we do it – and when - and the impact when we don’t anymore (ie long-term relationships).
*Also, tips on how to get flirty if you feel rusty etc.