What is the best setting for taking photos at a wedding and the reception?

[Skirball]

There are no best settings, it will always depend on the conditions and the photo you want to produce.

Me?  I set to either full manual or Av and set my camera to the exposure that I want give the photo I want to make.  But if you have to ask then I'd say "set your camera to the green square".  Sorry, but it's a vague question, so you're going to get a vague answer.

[cicopo]

As said no such thing as a best setting for all the different things you'll need to capture. I however recommend P mode rather than Auto and suggest you learn about exposure compensation & flash exposure compensation. If you have a decent understanding of the relationship of aperture settings & depth of field you may want to use Av mode too.

[TCampbell]

The camera is just a tool.  To get the most out of it, you'll have to learn how to use it.  While you can use it in full "auto" mode or "program" mode and it will do it's best, what makes a DSLR attractive is the idea that it makes it easy for you to take control.  

In the same way that buying a Steinway concert grand piano wont help you play better music if you don't learn how to play a piano, the camera isn't going to help you take great pictures if you don't learn the basics of exposure and composition.

I'd suggest you pick up a copy of "Understanding Exposure" by Bryan Peterson -- highly recommended for those just getting started.  Also the Scott Kelby Digital Photography series (I think it's up to 4 books in his set now) are also highly recommended.