Being cool and having confident body language aren't necessarily the same thing, but yes, guys that are cool tend to be confident and comfortable in their own skin. Looking back to when I was a supreme beta, one thing I can now reflect on is that I often wasn't comfortable in my own skin when out in social/pick up situations (big parties, bars, clubs, etc.), and my self-conciousness and low confidence, most likely caused me to be kind of awkward. This awkwardness and uneasiness seeps into your mannerisms, through your body language, posture, eye contact, and vocal tonality. As many of us know when first opening a woman, our non-verbal communication is almost more important than the content of what we actually say. You can have the most clever well thought out opening line, but if you come in awkwardly, look away (can't keep eye contact), and your voice cracks, then the girl is going to think your a straight up loser.
So how do you gain this confidence? I would agree with what Roosh said about: "I can easily tell a guy to not lean in or have a feminine posture, but that’s only half of it. The other half will magically come (I’m being serious) as his confidence goes up and he starts banging a lot of women. It simply falls into place." It hard to quanity/qualify or explain, but just with the more success you have with women, the more comfortable you become around them, and this is communicated to them through your vibe, which women are extremely perceptive of in an uncanny way.
Ever been through a horribly long drought, and you wonder to yourself, why you keep striking out? You're going out and spitting half decent game, but it just seems like you some kind of female repelent, which they can sense from a mile away. One the flip, you ever gone on a hot streak where it almost literally seems that pussy is falling out of the sky and into your lap? You're not even really trying and girls are drawn to you, their is this aura or vibe that you are putting off that is magnetically pulling them in, or not, or it's the opposite and they are put off by you. When it rains it pours my friends, but when it's dry, it's oh so damn dry...
This is one of the mysteries with women, there ability to pick up on vibes, there attraction and being drawn to guys that are getting laid a lot and have options with many different girls, and especially with attractive girls. This is something I could never figure out as an AFC beta and while I progress and develop and understand it better now, I still don't understand why the allure is quite so strong. Women want guys that are good with girls, period. As someone said (Entropy I think), experience breeds competence and confidence. It's hard to be confident and compedent if you've only slept with one girl and it's been a year since you last got laid.
Well, I appear to be very stoned and zoning out typing my thoughts, not sure if anyone will get through all this text as I seem to have wrote quite a bit. But final thoughts that might pertain to you and help some guys out right now are, as simple as it is, just relax. Relaxing and being comfortable are the biggest keys. If you are in a social setting and you are feeling any level of anxiety or self conciousness, it's going to seep into everything, how you act, what you do and say. When talking to women, as Roosh says avoid leaning in, keep your posture straight with you chest out and your head up. It is important to hold eye contact when talking, but do not over think it or do it, natural pauses and breaks will occur with conversation. Avoid letting your eyes dart around the room, look side to side or down at the floor, and try to not to stare at her tits if their popping out her shirt. Always be aware of your vocal projection, speak loudly and clearly with a confident voice, but please be aware, so that you aren't almost to the point of yelling. How you "deliver" what you say can be important to as far a vocal tonality, with pauses and emphasis on certain things, if you are trying to be funny, witty, make a point, or get to the most interesting part of a story.
http://www.youtube.com/watch?v=fl8c6FPq6mU
