what is the best way to shoot video at a wedding without lights, I have a canon XH-A1, this will be during a dancing scene. Thank you

It takes light to make pictures. The best you can do is shoot wide (since the lens stops down when zoomed in), shoot at 24f and at a 1/24 instead of 1/48 shutter speed, shoot wide open of course, and if necessary you can go up to a +12db gain, and that will create some grain but that's life. If you go higher than that, the grain is even worse. I did a wedding reception once for a friend and used a 2/3" chip camera (SD) boosted to +12 and it was still dark but you could see a few highlights on occasion.

Experiment in advance. Set up some situations at the light levels you expect. Try different shutter speeds and gain settings including those mentioned above. Decide what offers the best compromise for your situation and customer. Keep in mind that some folks do tolerate more grain than others.

And note that even a small amount of additional on camera light can make a big difference in the final image.

Frank,
I shoot the majority of my receptions with no light. I shoot 60i 1/30 shutter with 6db of gain. I find (and I may be corrected here) that if you reduce sharpness ala Truecolor preset and keep NR2 on high, you get a very manageable picture. I agree that 12db is acceptable if it's very dark because that's what they would expect it to look like. Dark. I always have my light which is a Canon VL10i and it does the trick if I have to use it, but I typically don't unless it is VERY dark. Here's an example. Wait until the reception.
Samone & Tony (http://www.grantphotovideo.com/samonetony) this was shot with the same preset all day and night.
Bill