The human face is such an interesting, and perhaps the most explored, subject in photography. This set of portraits is particularly dedicated to Michaela whom i think is gifted with an x-factor and a cheerful smile which can transcend from one mood to another in an instant. Taking a good portrait is not only choosing the right face. Consideration should also be given to selecting the appropriate background and good composition or cropping style as well as the lighting available at your control.
Sometimes a plain backdrop will work best like blank walls and other single color background to avoid stealing the attention of the viewer from the main subject.
If shooting indoors, it's better to use a flash bounced off from the ceiling to achieve a more natual lighting effect, though sometimes shooting with available light can do more wonders if you're projecting a certain mood.
If you want to emphasize the face, try shooting at least from the shoulders and up or just go near or zoom in the face to concentrate on the facial contours. Focus on the eyes as this can to capture the emotion and the enagaging gazes and glances from your subject to create an inviting feeling that draws the viewer into the picture. Positioning the subject in off-center often yields better results than merely placing her in the middle or center of the frame.
Talking to your model before taking the shots should put her in a relaxed mood thus, allowing her to smile sponstaneously to project a certain mood and expression. Take charge and give instructions if what you're seeing is not to your own liking.