my personal oppinion its not about just posture its about your facial expressions.
Usualy good posture is alfa posture, chest in front, proper spine like it shoud be.
Dont cross hands n stuff..
but facial expression is more important, that is by my oppnion biggest part of body language, I think you should have smile all the time! but not like

or
You need to have SET of smiles for a lot of situation.
For example you need different smile when you talk to a guy where you wanna show him that hes not boss if he tryst to be and you need to have smile for a girl where you want to show... that you are the boss
I cant make facial expression but you dont express same emotion so ill use photos on forum HEAD.
Look at gemblers diskret smile. This is sort of smile, you can see that he is not worryed or in some sort of disconfort hes like 'im the boss im ok with you but dont fuck with me"
Its not fullsize smile but its sort of smile, Same sort of smile have carlos xuma.
Imm ok with you but dont fuck with me, and im not in any sort of disconfort making that face, expressing that emotion. We are ok but wach out we easly cant be.
Getting that if you are not in any violent society is not hard. IF you are not gang member or in prison. Cuz there is nothing except yourself stoping you getting that attitude and it wont hurt.
So why smile? you allways wanna send a positive message. Eaven if you are in trouble with someone. You dont ever ever wanna send message of some sort of hate, cuz hate is weakness.
So that + normal posture. strong regular posture like man should have sholders back, chest front proper spine.
I like to tilt my head a bit to the side.. dont know why... i just think its cool
