Try a Wink

To send a message to someone you´re flirting with, give a wink. A wink is as warm as a smile, but more flirty. It´s also a little more obvious, if your flirtee is likely not to understand that you´re smile was meant for him or her.

If you're not good at winking, try practicing in a mirror. If you watch people flirt in the movies, you'll see there are ALL sorts of wink styles that can really send a strong message. Just practice!