You should be aware that it is a very risky business. You leave yourself wide open to being sued for damages if you get it wrong. There is nothing more dangerous than a woman who has had her wedding day spoilt because the photographs turned out to be a failure. I am not saying yours will, just be aware. I understand that most sensible wedding photographers will carry insurance.
If you are not being paid you are still bound under a verbal contract if you accept an invitation to do the work.
I photographed my Daughters wedding and I know how stressful it can be. With digital at least you do have the chance to review the image on the back screen and take it again if it is in doubt.
One other tip is to use the Auto Bracketing feature and take three images of each shot if the lighting is dodgy.
-------------------- David.
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www.flickr.com/photos/monobod/ -----------------------------------------------
I see the world thro' a viewfinder, but the world watches me via CCTV!