Maybe you like to read the following tutorials / articles in conjunction with your trials in poser.

Not directly Poser related but light in general:
http://www.itchy-animation.co.uk/light.htm
http://www.huevaluechroma.com/021.php

Poser related:
http://www.drgeep.com/NPU/Directories/dir02.htm
(on the lower left side of the graphic on that webpage you'll find the light tutorials)

When working with point or spot lights:
Search for ISF shader (inverse square falloff shader) made by Bagginsbill if you are not using Poser 8. You can attach that shader to the lights. By doing so the lights behave more in a natural way.