Well since I am rendering at the moment (Bryce 6.1). All I can write for now, some of the tools for realism. First, is grabbing (making) an expression. A smile along with proper eye expressions go together. Majority of images I did see, are all serious, no expression at all or could I say nothing (no work at all). Watch how some people smile in reality, that is how I made the one above, by using an image from a magizine. Teeth coloring is a key as well. The default  teeth coloring is not correct and need a color balance. Eyes are a huge issue for realism in poser. My favorite character and that I used was by Vali (Larisa), and then used Real skin shader, and then Occlusion master. Adjusted the Baising in the material room.  Lighting....well, on the image above is two lights. One IBL AO, and other infinite. Both were very difficult to balance out, although can be done if you know what your doing. In light settings "Shadow Min Bias" and also in the AO settings "BIAS", "Max Distance", and other "Bias" settings, need to balance out. All about Biasing. If proper adjusted with lights, you will acheive realism. Still on the learning curve of all I wrote. Only one problem I missed was the nostrils. I decided after to work on something else after a few days of constant renderings of image above. Image above I do not like, but the realism shows (lighting, texture).