I once worked with an art director who would not hire a model outside of NY.  His words were, "other models may look good but they don't know how to move".  Too many models think that looking good is the end-all but really it's just the beginning.  When you go on a shoot, it's rather a performance...like with my band ( www.bbymusic.com ).  Just knowing how to play isn't good enough.  You actually have to get up there and do it.
So...what really is a pose?  I thought about this for a while in trying to convey to a model what I needed from her.  I narrowed it down to a pose being a replication of an actual point of action worthy of being photographed.  On a journalistic project, I will often scope out scenarios and wait for the perfect point of action...as Ernst Haas describes as the "decisive moment".  The point when a baby smiles, a child laughs or cries or a mother's love is conveyed in a single glance.  When we take this philosophy and break it down, it's no wonder that most emerging model's and photographer's portfolios quite simply ($%#*).  Where is the feeling?  What are you trying to convey?  Most models don't pay any attention to the art of trying to replicate real life emotions and movements...but I can tell you for a fact that the one's who are successful are true masters of their craft.  What is that exact look of when a guy and a girl glance at each other knowing they like each other in a single glance.  Simple laughter...but not squinting.  Simple playfulness for the camera that is not contrived looking...even though you're not really in the best of moods.  Imagine the camera as being a mirror to another world because when you look at a photograph and the conveyance and emotion with the subject is "seemingly" pure, the impact is extremely powerful.  The viewer of a photograph should always have some type of interaction with the subject...regardless of where the model is looking.
I once worked with a male model who's job was simply to be in the backround walking up to a model who was the main subject.  The space he could work in was very confined but he replicated the look of walking and throughout the shoot, he was walking in place...looking completely realistic, confined to a 2' x 2' spot.  I was really impressed that throughout the shoot, he never once looked like he was faking it. 
This brings up a very strong point.  There is nothing worse than a contrived, fake looking pose.  Had that model's walking in place looked fake, it would have blown the whole shoot.
There are models out there who can do no wrong in front of the camera. They make photographer's seem brilliant to the art directors and editors.  I've often had the experience of putting a girl in a scenario and as soon as they are at their mark, I'll be able to shoot.  They'll ask, "what do you want me to do" and I will respond "exactly what you are doing".  They'll say, "but I'm not doing anything" and I will respond, "we'll keep doing just that".   On the other hand, I once worked with a Brazilian model in NY that had her whole repertoire lined up and as soon as the camera started roling, she would go through a whole list of looks that she had rehearsed down to a T.  It was kind of funny at times that if she gave me a look and the lights didn't flash, it would seem to upset her...giving me the "what was wrong with that".  My response to her was that there is only so much film in all of NY and that I was getting all that I needed and then some. 
It all comes down to the phrase PROFESSIONAL model.  So many people disregard the word professional as being the most important part of the term.   Actors and musicians just don't get on stage without practicing their craft.  So many emerging models think that it's just a matter of being 5'10" and beautiful.  You will find that once you go through the ringer of being with an agency, actually being a self supportive, working model takes a whole lot more work than just being beautiful. 
Personally, I don't like to tell a model what to do.  I like to convey to her the feel of the shot, the lighting, camera angle, etc and then see what she will bring to it.  When I have to get down into actually putting the girl into poses, that's generally a failure on the model's part.  The model IS an actor and as so many great directors have said about monumental movie roles..."so and so brought a vision to the role that I never even thought of".
There is no doubt, this is hard work.  To actually make it as a model is a monumental task.  Aside from making it, just simply getting to the point of representation and doing a job here and there is monumental as well.  Every model that I've ever known who has "made it" has taken it upon themselves to be proactive in every manner.  If an agency likes you at an open call and they want you to test, they will be impressed if you have images for them next week versus next month.  If they can tell that you are actually going to work to get things roling, they will work for you.  If they feel you aren't going to rise to the occassion, their attitude is that "we get 100 calls a day".
Just a few thoughts to digest.  Read the fashion magazines and study the pictures.  Understand why the girl in the picture is there and what can you possibly do to get there.  Test as much as possible because even though the crappy test with XYZ photographer was a disaster and you can't use anything from the shoot...chances are, you might learn something that might help you in a critical moment down the line.