Observe if the person looks at you frequently and if so, chances are he is attracted to you.
People display a tendency to send a lot of looks to the person they are attracted to. Avoid taking every gaze as a sign of attraction though. It’s good manners to look into the person’s eyes while speaking during official discussions or meetings or when introduced at a gathering; these look-locks are not signs of attraction. Watch if the person looks at you without any such reason, for example he gazes at you when there is a speaker on stage. He quickly averts his gaze when you meet his eyes, or keeps staring at you till you feel his eyes and return his look. You can safely conclude that he is attracted to you if you catch him behaving so on more than one occasion. These signs are true for women as well.
Watch her behavior around you.
If a girl finds you attractive, she becomes unusually quiet and self-conscious in your proximity; this may seem strange, especially if the girl is usually an extrovert and cheery in behavior. The reverse – becoming excited and lively when around you -- can also be a sign of attraction. The key is to take note of any behavior contrary to the girl’s usual behavior, when you are around. Another girly gesture that indicates attraction is adjusting her hair several times when in your presence to make it look more presentable. If the girl is attracted to you, she is also going to laugh at your blandest of jokes.
Keep an eye on a guy that tries to impress you in a crowd.
He talks about his brand new cell phone or his black belt in karate, and turns your way to see if you are listening; another tactic is to crack jokes when in a crowd, especially if you are nearby, and then look at you to see your reaction. Consider the strong possibility that he is interested in you if he seeks you out in a crowd and starts talking to you, or if you find him listening to even your shortest of sentences with rapt attention. Learn if he’s been asking about you to your friends or colleagues; this is a sure sign he is drawn to you.