Have you ever heard the expression, "mirror work?" As a model, you not only need to know what it is, you need to be doing it at least once a day.
Mirror work is simply developing muscle memory for your face and body so you can do it naturally when called upon for a shoot.
The first part of mirror work is to practice your poses.
Just as baseball players practice their swing so they develop muscle memory, a model needs to practice her poses for the same reason.
For at least once a day, stand in front of the mirror and learn the poses in which you look best and the ones you look the worst. Ask yourself how you feel during each pose? Does it make you feel good or bad? Does your butt look big or does the pose bring out the right line of your body?
Find 10 poses that you think compliment your body and practice them until you can do them in your sleep.
The second reason for mirror work is to practice your facial expressions.
Your smile is extremely important as it's the most important facial expression you have. Most people don't smile in a way that compliments themselves. They usually squint too much or show too much of their gums, both of which look bad.
Smiling in front of the mirror will allow you to "feel" your face when you smile as you should.
You should really only do these exercises for 5 minutes at a time so you don't lose concentration on what you're doing. Of course, doing them more than once a day is encouraged.