Without seeing any images it's really hard to say if the issue is with your render settings or with your lighting setup.

I can strongly recommend the render preset scripts found on this thread, http://forum.daz3d.com/viewtopic.php?t=177995 as a great starting point. I've been really happy with the final quality setting from these scripts plus it makes it super easy to quickly flip from draft or medium while you're fine tuning things before flipping to final when you have things dialed in.