Pendrith, here's a quick setup you might be interested in that gives pretty good results. Load the UberEnvironment base and set it up for a low level ambient that also gives you your Ambient Occlusion. After loading the base, set it to 4x High, then in the properties, adjust the light level down to something between around 30% - 60% usually (varies depending on what you are doing.) Consider setting the color to a light off-white with a slight bluish cast. Put in a distant light for outdoor scenes and call it sun/moon... This is your key light. Set it appropriately, and consider a light off-white slight yellowish cast and turn on ray traced shadows for it. Set the softness depending on the scene. For indoor lights, the setup can vary considerably, but generally there will be one key light, set with ray traced shadows, other lights you might want ray traced shadows on but usually not. I rarely set more then one light to shadows, but sometimes you do want to. Just realize, the more lights set to cast shadows, the more potential conflict between shadows and the longer the render time. To cut down on conflicting shadows, it's often a good idea to soften them up considerably if they aren't the main light. I hope this helps.

*side note, lights in DS that don't cast shadows will go through solid objects, so if you have a light inside something and it bleeds out where it shouldn't, you might need to turn on shadows for that light.

Btw, if we are off-base and you know what you want to do and all of our advice is not really helpful, then sorry.. good luck either way :)