Indoor Event shots w/Flash

I'd like to hear some recommendations for shooting indoors, typically people. I'm using a Canon 20D, 580EX (on the camera).

-ISO?
-Av, Tv, M mode? (I'd like to capture the people well but also have the background show up)
-f/stop?
-shutter speed?
-flash angle? (I typically keep it 45 degrees & have the white card out)

Thanks.

To answer your generic question the basics one should follow are:

• Have an apeture in mind first for the DOF and bokeh you desire
  
• Choose a shutter that is greater than the focal length of your lens AND that can stop your subject's motion (assuming no tripod)
  
• Choose the ISO that allows you to use the aperture and shutter chosen.
  
• Tweak shutter or ISO to get the histogram right.

First - get the flash on a bracket. A camera rotator is my preference. With a Lumiquest ProMax System.

Camera in M, ISO 400 (depending on ambient light), f-stop sufficient to cover your required DOF, meter for ambient keeping an eye on your shutter speed.