Flirting is a natural behavior when  you are in love, and you naturally show your love and are attracted by someone by using some body languages. Be aware that flirting is not artificail and  personal behavior, but natural and general. Wonmans have creative and various types of flirting, and thier body languages are not easy to read. Some common behaviors that womans do to exprese their love naturally are that they play with thier hair or neck and crossing legs or shoulder. In addition, womans try to keep eye contact with the man and touch mans body or hair is a sign that she is flirting. Men also have similar types of body languages like keeping eye contact or try to touch her body, but there is a different behavior when men is flirting. Nervousness is a one common sign that men is attracted by someon and trying to attract her. Men generally "try" to talk with girl that he is intersted in, and if the man looks scared of how she react, he might be trying to flirt her.

http://www.buzzle.com/articles/flirting-body-language.html