Eye contact is a classic sign of flirting. If someone glances in your direction more than once, it's a tell-tale signal they are flirting. If someone keeps their stare fixed on you they are making it obvious they are flirting. Sometimes instead of making direct eye contact, a person flirting will conduct a "once over" and check someone out from head to toe.
If someone touches you, it is a signal they are interested in you. Touching can often be inconspicuous. There are many forms of touching that indicate flirting. A common way of flirting through touching is if someone gently puts their hand on yours. Another way to tell is if during conversation they lightly touch your arm or shoulder in response to something you said. Touching is an effective form of flirting as the mind cannot help but respond to contact in a positive manner.
If someone pays you compliments it is a surefire indication to know they are flirting with you. Compliments often come as a way of catching someone off guard. A person who pays compliments is showing that they are really paying attention and have taken notice of you. The best flirting compliments are those that are enthusiastic, from the heart, and authentic.
Smiling is another signal that someone is flirting with you. According to bodylanguage.org, there are two ways to tell a true smile. With a real smile, the edge of the mouth bends upward and outward and the wider the smile, the more teeth that can be seen. With a true smiling face, the outer areas of the eyes also become wrinkled into "crow's feet" and these lines can not be consciously manipulated. A forced smile will not have such lines, according to bodylanguage.org.
If someone you have never met before comes up to you and starts a conversation, chances are they are flirting with you. Flirting conversation could be something as simple as someone saying hello, asking for directions, or making a casual observation. If the person shows an interest in what you have to say and maintains good eye contact, they are displaying that they are drawn to you.