Flirting is a way for a guy to communicate that he is interested in you without actually saying so. It is usually displayed in body language through gestures, facial expressions and posture. The behaviour is instinctive, and being able to interpret it is a useful way to find out if he's attracted to you.
The Way He Looks At You
Eye contact is an obvious way of flirting to get someone's attention, and if a man looks at you, looks away and then quickly looks back again, you can be certain he is attracted. If he looks at your mouth as you're speaking, this can indicate a desire to kiss you. Men are generally more visually stimulated than women and will respond to what they can see. Watch for a guy quickly looking you up and down. This is a sure sign he likes what he sees and if he also raises his eyebrows, he's definitely into you.
The Way He Touches
Men commonly resort to preening behaviour when they are with a woman they like. This includes stroking the chest, adjusting clothing or touching their hair. These are unconscious gestures that show they want to impress by looking their best. A strong indication that a man is flirting is when he touches you. He can start by subtly brushing your arm or leaning his knee against yours. If the response is positive, he might move on to a lingering touch on the arm, leg or lower back.
The Way He Stands
A flirting posture that many guys adopt is the "Alpha male" or "macho" pose. He will stand tall with his chest out and stomach pulled in, mimicking the way animals sometimes assert their authority. If he stands square in front of you with his feet forward, this shows interest while blocking out the competition. If he hooks his thumbs into his belt loop this is a clear sign he finds you attractive as he is subconsciously trying to draw attention to his crotch area. "Mirroring" is another sign that a guy is flirting with you. He will unconsciously copy what you do by mirroring your gestures, showing an affinity with you.
The Way He Speaks
Agreeing with what you say and nodding is an indication that a guy is interested. If he leans in to whisper in your ear, it shows he wants to get close to you. Offering to lend a coat or sweater if you are cold shows he wants to please you, and asking you questions about yourself allows him to get to know you better while engaging in flirtatious chat.