Professional models need both an understanding of common poses as well as the ability to take direction. Professional photographers don’t want to have to guide models through every step of a shoot, it kills the moment.  To be at the top of  one’s game requires constant learning and practice. So  models need to practice poses until common poses become second nature, they acquire what is called muscle memory.  

There are exceptions to every rule but for the most part professional models know five critical rules for posing:

1. First never keep your body straight on to the camera.  No matter what size you are it makes you look too wide or just plain fat.

2. No straight lines or in other words if it bends bend it.

3. When laying or sitting put your weight on the cheek away from the camera.  This prevents the force of gravity from misshaping and fattening your legs and butt.

4. When arms or hands are touching another body part do it lightly.  Pressing one part into another deforms your beautiful shape and increases shadows on the skin.

5. In most poses your fingers should  be extended to prevent your hands from looking like you lost some fingers.