It's in the Eyes
One of the most common signs of love at first sight is total infatuation. If the guy cannot take his eyes off you, it can be a good sign of love at first sight. Often such infatuation also results in other facial changes, such as a goofy grin or an open mouth. The person sometimes stops where he is and just stares like a deer caught in the headlights.
Sometimes love at first sight results in an energetic assertiveness to talk to the object of your affection. The assertiveness can range from very enthusiastic conversation to downright declarations of love. Be careful, because some assertive men are not in love and are just being assertive for other reasons.
Shyness can also be a sign of love at first sight. The inability to hold eye contact and difficulty talking can both be signs that the person is in love. The feelings the man is having can paralyze his normal social functions and revert him to the state of a child. He might find it difficult to socialize as a result.
Awkwardness is a very good indicator of attraction. Because of the feelings generated, the man places a great deal of importance on making a good impression. This results in the man not acting naturally as he attempts to execute new behavior he believes will impress the woman. The man's reasoning and logic centers are impaired by the encounter, and he has difficulty being "smooth."