Desire

Women by nature have the skills of flirting and drawing attention to themselves. Therefore when a woman is attracted to someone it becomes easier to notice these signs which are five times more than what a man displays.

Body Language Attraction in Eyes
When a woman is attracted to someone she will try and maintain prolonged eye contact. If she observes you looking at her, she will hold your gaze for 4-5 seconds then look down and immediately look at you again. This is a sure sign that she is attracted to you.

So also when you see her for the first time and she is interested in you, her pupils will get dilated. This will lead to a doe-eyed softer look that is sub consciously brought about to show that she is attracted to you and wants to be able to see you better.

Leaning In
If she is attracted to you, she will want to show that she is there for you - interested in everything you say and basically holding on to your words - thus subconsciously she will lean into you when you talk. Many a times she will lean against something to show the curve of her body.

Licking Lips
Next time observe carefully and you will see that when a woman is attracted to someone her lips will become slightly flushed because of the blood rushing to that spot. Moreover, she will lick or pout her lips because they tend to get dry. She might even apply lipstick in front of you to take your attention to her lips.

Facial Expressions
When she is attracted to someone, a woman will always smile wide and full. Smiling not only with her mouth but her eyes and cheeks - her eyes will literally twinkle. So also, she will tilt her head sideways to create a pose. More on facial expressions.

Involuntary Touching
A woman will touch parts of her face like the lips or cheeks or her neck to get your attention to those places; it is a subtle way of saying she wants you to touch her there. She also plays with her hair.

Smoothing Clothes and Flipping Hair
Once she sees that you are in the same room as her, you will more often than not, find her smoothing out her blouse. So also she will flip her hair and expose her neck which is a submissive way to say that she's vulnerable and is not threatened to let you in on her vulnerability.

Posture
Her shoulders will be facing towards you and her back to everyone else, thus showing that she has eliminated all competition and finds you interesting enough to be focusing all her attention on you.

Open Palms
Observe her palms the next time you meet. If they are wide open so that you can observe them, it means that she is very vulnerable to you. This is her way of submission, but on the other hand, if her fists are tightly closed it means she doesn't trust you enough.

General Reactions
If she laughs at every small thing you say even when you know it's not necessarily that funny, you'll know she's trying to boost your ego and make you comfortable in her presence. So also she will subconsciously try to touch your arm several times.

Mirrors Your Moves
If you find that just as you lift your glass, she does too, or when you scratch your nose, she'll do the same - She's subconsciously mirroring your moves. She's trying to show that she's attracted to you and wants to do whatever you are doing.