Taking pics at a friends wedding?

[Mark]

Some ideas - (I'm not a pro either, but these are the ideas I had after reading your post)

Divide up the work. If one of you shoots the guests, the other concentrates on the bride, groom and immediate family. If one of you does the ceremony, the other does the celebrations. That kind of thing. Then neither of you will be rushing around like a headless chicken chasing everything.

I never use flash unless I absolutely have to, so I'm not going to be advising on that. If you have time before the wedding, have a look at Joe McNally's site. He's a master with lighting, so you might get some good hints from that. If you decide not to use it, then you'll want to shoot either in full sun or full shade, but try and avoid mixing them up because the dynamic range will throw your camera for a loop and you'll have a merry time trying to fix it in post. Don't shoot people who are looking into the sun, because they'll squint, either consciously or not.

Take several of the lenses to be safe. The 50 on a crop body like the 40d could make for a nice portrait lens, but if it's a bright day and you want to shoot it wide open you might need an ND filter on it if everything's outside. The wide zooms will be good for group shots. The 75-300 could be nice for getting shots of the celebrations from a distance (i.e. candidly). 28-105 and 24-85 are similar ranges so you probably won't need them both unless you have a particularly good reason for carrying both.

What I would absolutely recommend is shooting RAW. Use a memory card with a decent capacity (or use a normal one and carry a lot of spares). RAW is important because it gives you more room for recovering highlight details, bringing out shadow details, and generally is better for correcting excessively over-or-under-exposed shots. It can also save you if you get your white balance setting wrong.

Carry a spare battery, at least one, or two if your current one is weak. You'll probably be taking a lot of shots.

Think of anything that could go wrong and come up with a fix for it (example: memory card gets corrupted, something goes wrong with camera, it rains, etc).

As your friend understands that you're not a professional, you'll hopefully be able to enjoy shooting the wedding. I've not done it before, but I'm told that it can be a lot of fun or a lot of stress depending on how you go about it!