There's a lot of threads that go back and forth, I don't think there's any one good concise tutorial.  Some key settings and techniques (at least for me):

• Enable Raytracing in render options
• Set Render Options: Raytracing Bounces to about 8 (that's what I use, experiment with it)
• Set Render Options: Irradiance Caching for speed/quality you like (I leave it at 1, oddly this is both faster and better-looking than higher values)
• Set Render Options: Tone Mapping mode to HSV Exponential (I think that is the default) with an Exposure of 2.2 (this value is arbitrary and happens to look good, it's not the same as a Gamma Correction value of 2.2; Poser 8 still doesn't do Gamma Correction and these features aren't doing the same thing)
• Enable Render Options: Indirect Lighting and experiment with quality setting for speed/quality you like
• Start using a fully enclosed polygonal environment that completely contains everything in your render scene (I made and use this one for studio style rendering, there is also Bagginsbill's Environment Sphere; if you don't fully enclose the render scene then you're missing the point of Indirect Lighting/Global Illumination)
• Stop using Infinite lights for anything but simulating the sun, and don't use more than one in a scene
• Start using point lights and maybe spotlights; point lights are very good for presenting an evenly-lit image where the light spreads around a great deal, while spotlights tend not to bounce around nearly as much.  Bottom right image in this pic (nudity) is lit with a single spotlight, the other three are lit with two point lights each.
• Stop using depth mapped shadows, because they are poo; set all shadows to cast Raytraced shadows.  Never use any lights that don't cast shadows! 
• Set shadow blur radius for each light to something above zero (I use 5.0 most of the time); set Shadow Samples for each light to 30 or more (I use 60, probably overkill); set Shadow Min Bias to something very small (I use 0.05)
• Nearly every material in the scene will need some attention, particularly the Diffuse_Value setting; you want it to be set to lower than 1.0 (the default) to simulate light being absorbed by a surface.  This is a pain to set by hand, so here is a script to set it to 0.8 for all surfaces in the scene.
• The Ambient_Color and Ambient_Value properties of a material will now actually emit light (glow) allowing for some pretty cool effects (look at the girl's right hand holding the gun in the lower section of this pic, illuminated by the glowing parts of the gun)
• If you've been using Ambient Occlusion, consider just disabling it, as Indirect Lighting (IDL) produces a similar effect but in a much more realistic way; if you do leave it enabled, you can turn it way down from what you needed it set to in older versions

There's other stuff but imo those are the big key things.  Attached is my default scene that I start every Poser 8 scene from, which relies on the render room prop I mentioned earlier.  Right click the attachment -> Save -> rename and remove the '.txt' extension, it's a zip file.  Have fun :)

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