The combination of aperture, shutter speed, and ISO setting controls the effect you get in your photograph. Ultimately it depends on the shot you want, and in any situation you someone may want to use a different combination than you, but knowing the basics helps. Now go read the manual and experiment with some of those extra buttons on your DSLR.
Did these help at all?
Shameless plug if you have a moment: Some of my photos on Flickr