Even the ancients claimed that you have to pay attention to a woman’s gestures instead of what she says.

Watch her fingers carefully.

If she pushes her fingers through her hair, she is looking to get your attention. Clean and neat hair is as important for a woman as acceptable height, wide shoulders and biceps for a man. The way she touches her hair is also very important. It tells you information about her temperament. If she does it slowly you have encountered a cunning expert of the art of love. Quick, nervy movements disclose impatience or embarrassment.
If she touches the edge of the glass with her fingers, Freudian psychologists often interpret it as a sexual sign. This theory is supported by the women themselves, who claim that they deliberately pet the glass, in order to call the chosen man’s attention upon themselves. Elegant, caressing movement is a sign of intrinsic calmness, self-control and waiting, so sit by her. Her beating a rhythm on the glass with her nails is a sign of impatience or a broad hint of SOS, which she’s sending to her boyfriend, who is fighting for another Bailey’s at the bar.
Note any physical contact.

If she touches you in any manner, this is almost always a good sign, with the exception of the event in which she is striking you and telling you to get out. If she is lightly touching you on the arm while laughing, or in general just finding any way she can to touch you, bump into you, or grab you, then she is almost certainly interested.
Check out her hands and arms.

If she leans on her hand with her chin and her eyes seem to be thinking, it’s not always the sign of her being impressed by your appearance. Generally the woman tries to answer her own question this way: "Does this guy deserve me" You know the answer, but the lady needs time. If you want to help her make the only right decision, be politely determinate and determinately polite. Flash your sense of humor as well.
If she sits back with her arms crossed together, this is the worst possible thing you can encounter when out hunting. This gesture is evidence of the fact that you’ve made the worst impression of all on the woman and she doesn’t trust you at all. Nothing helps here, neither refined jokes, nor nice, muscular body.
The way the woman herself thinks of her hands is also very important. If she stares at them for a very long time, it may imply that something angers her (perhaps you?). If she beats the rhythm on the table or the bar means a similar state of mind.
Look at the lips.

If a woman wets her lips quite frequently, it’s either out of habit or desire to get you to pay attention to her lips and sooner or later kiss her.
When a woman is biting your lips, do not interrupt her – everything’s alright. But if she’s biting hers, you may assume that she’s nervous. Why? Perhaps you are staring at her too inquisitively.
Eye the eyes. According to famous experts of the topic and authors of cheap romantic stories the fast movement of the eye-lashes is the sign of women who like to conquer men of their own accord. Besides they are emancipated, who like to take over the duty of initiation. They aren’t waiting for your jokes and wide smile. They undertake to initiate. The only problem with such ladies is that not all of them will enjoy herself in the role of the doped out game. But if you don’t mind losing the role of the hunter, swallow the bait. Also, note her pupils. Basic biology tells us that when we like something (or someone) our pupils expand (dilate). When we don't like something, they contract. If her pupils are big, it may be a sign that she likes you, or likes what you're saying. On the other hand, if her pupils are small and pointed, it may be a bad sign. However, this method isn't foolproof. If it is really bright outside pupils contract naturally, regardless and if you are somewhere darker, they naturally dilate.
Check out the legs. Researchers of body language emphasize that when a woman frequently crosses her legs or let them swing, is also a sexually charged movement. The strongest of all these movements is when she opens her legs without meaning it. It’s a classical Freudian opening symbol. A contrary sign to this is when she puts her legs together.

Check to see if she turns away quickly when you turn to her direction: this can be a bad sign, or she just doesn't want you to catch her looking at you.

Not all women have the same body language! Not all women correspond well; it may be due to shyness or any other cause
Women may be offended by you checking them out.
Refrain from assuming that seemingly sexual gestures mean the girl wants you. If you make advance and she's not looking for that, things will probably not end well.
Also do not stare at the woman's cleavage if she has it partially exposed. Some men when talking to a "sexy" woman have a very bad habit of doing that. Any woman will take offense when she notices that your eyes are wavering (Especially on the very first date).Try to avoid the temptation!
Small talk is the key. Dont talk about your past previous relationships. Or a 3 hours talk about how you live or your job. Get her to do most of the talking. She'll think your a good listener.