Welcome to Posering.  1. The default lighting SUCKS !  there I said it .  The default three lights are colored and affect the skin textures , and all three cast shadows.  You may get better control of your lights if you change one at least to a spotlight, and have only one light making shadows . 

Any book on photography studio lighting will be a help, its not exact because of the way Poser treats light but a good start. 

You will also get lots of opinions on what works best, just try a few things and go with whatever looks best to you.