Well from what I understand, body language, tone and dress is all supposed to just shape up a person's first impression of you and also, congruency and sub communicate what type of person you are.
From some research I read somewhere, people will stereotype you within the first few minutes. This is where dress, body language and tone come into play. Lets say you see a smarty dress, well built, tall, stronge cheekbone and strong jaw line, with a deep voice, your first opinion is manly and "alpha"? Now you see a a guy with a bad haircut, hunched back, hands always crossed, clenched fists, glasses, bad acne and a squeeky voice and talks really fast, your first impression is a nerd.
So basically most of that, gives you a warmer approach, depending on the girl. I mean, if you look/act like an abusive ex, she'll probably stereotype you as a girl-beater or something.
Apparently, according to numerous body language sources, women are expert body language readers, due to being the child bearer. Needing to know the needs of a crying baby is important for its survival, so it was necessary for women to know what babies want, from their body language, hence it built into their system as evolution carried on.
Women, will often closely listen to their "women's intuition" which happens to be what their gut tells them, from what they pick up off your body language and your vibe. This again fits into stereotyping but also the kind of mood a girl will be in, as if your body language is very threatening, then she will act defensive, If you have very open body language and an upbeat vibe, then she'll probably be more comfortable and chill around you.
As for congruency, you personality might clash with whatever stereotype you were assigned. This is minor but it counts. There is also the fact that, sometimes your body language is different to other times, giving a sense that something is dodgey. Also not too big a problem I guess.
All of the things related to body language, tone and what not all affect a subconscious perception of you, so it can probably lead you to warmer approaches, more chicks feeling comfortable around you, and probably help you weed out time wasters and save some time.
Oh, also Body language is often used to detect attraction signals, IOI's, if you will. I suggest not rely on body language for that purpose, because unless you learn a lot about body language, you'll find a lot of attraction signals are very misleading and you might fuck up here and then, then get frustrated and give up on body language.
Hope that helps
