You can't create your vision without communication, here's how I do it efficiently.
There are nearly an infinite number of ways to accentuate a person's strengths and minimize flaws or insecurities, it would be impossible to catalogue them all, but what we (as photographers) can master is quickly and subtly getting our clients into the most beneficial poses.
Due to human anatomy there are only 4 ways to move our heads, so lets name them:
1 Turn, this is simplest to explain, it's the same left and right motion we use to look around a room
2 Raise/Lower, this is the motion to look up at the sky or down at the ground, still simple
3 Tilt, this is like placing your ear against your shoulder, people will usually tilt their heads slightly when you ask them to do any other motion, which is why I usually fine-tune the tile last.
4 Turtling is what I have decided to call the last motion, it's not always necessary, most effective generally with large subjects. To achieve this, you want to keep the first 3 above still, and push the plane of the face straight forward toward the camera. In engineering terms, you will cantilever your neck over your chest. This has the effect of drawing up the loose skin and/or fat in the neck. It does not help unless the face is pointed toward the camera, do not use this technique for angled or profile portraits!
Now that you know these techniques, the best thing you can do to improve your communication with your subject is to have a "Posing lesson" at the beginning of your shoot. Things to cover:
1 What words you will use when you need them to do each motion
2 Show them how you will move your hands to indicate the direction you want them to move
3 Warn them that posing often feels awkward, but if they just wanted to casually stand there, they wouldn't have to pay a professional ; )
In Posing 102, we will talk more about what to do with your newfound directing skills.