Body language in business

I've been looking into how body language can make an impact in the office/workplace, and how what you're saying to another collegue could be completley different to what you really mean, which can be unhelpfully given away through the involuntary movements of your body.

Most people have heard that eye contact can show an interest in a conversation, that a smile will relax a group of people, but I also looked into how a simple thing like a sigh or a yawn could be a sign that someone needs some help, or at least some coffee... a gesture in itself which would probably be more helpful that reading books on "how to improve your body language".

A thought did occur, should people read info on how to ensure other people that we are interested in what they are saying or that we like them? Should there be so much time spent on something which is not always backed up with the truth? The dynamics within a workplace start as early as when we are in primary school - you dont talk to the geeky kid because then you will be viewed "uncool". Similarly kids will avoid the boring one in their class because that person simply is not interesting enough. The best, or at least most important part of our actions when we were young was that there wasnt such emphasis placed on the pretence of a smile or an 'open arms' approach: if we didnt like the boring kid, we would tell (s)he very bluntly.

Though, because (most) adults dont have that guilt & conscience free nature of their younger years, we must try to match our body language to what our mouths are saying (a few examples below).