The main thing to look out for is objects blocking light. I would personally ignore suggestions to turn off shadows, since this usually results in poor image quality. No offence to anyone who offered that suggestion, but look through the gallery and notice how many of the less attractive images are missing shadows. The biggest problem is that Poser doesn't have a viable global illumination solution, so you're limited to either scanline or raytracing, both of which are outdated now. The best way to get around this is to do like LesBentley suggested, and add low intensity lights to areas that are getting too dark. If you must lower the shadow opacity, I would recommend staying between '0.500' to '0.750'. Additionally, if you are using Poser 5 or 6, strategic use of the material room to add a bit of self illumination to your objects can help. Poser doesn't have everything (yet), but it usually has some way of reaching a compromise. When that compromise isn't good enough, there's Carrara :)