Read this tutorial:
http://www.itchy-animation.co.uk/light.htm
Great resource and explanations of how light works, etc.
Well worth the read and bookmark.
BgDM
awesome website, thanks for the link! really usefull information in there.
this is an excellent one. i read this a while back when first starting to use Yafray.
I’ve seen this before. But this time I bookmarked it.
Great site, but its already been posted:
https://blenderartists.org/forum/viewtopic.php?t=57129&highlight=
However, I’m sure it’ll be of more use to people being posted on this forum.
Thank you. 
Since i’m new to blender everything is usefull, since i registered here i made plenty of bookmarks
That is indeed a very useful article, I found it a few days ago and learnt alot from it.
I found it very useful… 
LIGHTING
-
Lighting Tips by Kory Heinzen (www.3Dtotal.com):
http://67.15.36.49/team/Tutorials/kory/koryslight1.asp -
Lighting Glossary and 3PT lighting:
http://www.myholler.com/147online/handouts/lighting.pdf -
3PT lighting by Jeremy Birn:
http://www.3drender.com/light/3point.html -
3PT lighting by Jenn Downs:
http://67.15.36.49/team/Tutorials/Jenns3pt_tut/3ptlighting.asp -
3PT lighting by Andrew Whitehurst:
http://www.andrew-whitehurst.net/3point.html -
Siggraph Paper about Lighting and Scene composition:
http://www.siggraph.org/education/materials/siggraph_courses/s96_course30.pdf (save as) -
Matching Real World Lighting by Andrew Whitehurst:
http://www.andrew-whitehurst.net/fx_light.html -
Daylight (Carles Piles and Jeremy Birn):
http://www.the123d.com/tutorial/c4d/daylight.shtml
http://www.cgtalk.com/showthread.php?t=154128 -
Effective Scene Lighting for CG Space:
http://www.ap3d.com/betterspace/betterspace-tut-12.htm -
What does GI mean?:
http://www.richardrosenman.com/global.htm
-Complete lighting overview:
http://www.itchy-animation.co.uk/light.htm
i’ve seen that 
bookmarked now! pretty nice indeed.
here’s another good one: