When it comes to deciding how to light as portrait and have it come out looking professional, an understanding of lighting is required. It is always good to understand the “rules” and then when comfortable with them, experiment and create. This Classic Lighting Guide introduces the in lighting patterns commonly used as well as explains a bit about light properties and the concept of F-stops as it pertains to determining exposure and show intensities for your subject.
The above guide will help understand how to light your subject. Check out this video for assistance with posing! Good luck and happy shooting!!