Here's Gary Fong giving a quick rundown on using a Canon Flash.
One reason I blog it is because he gives a comment I agree with: many people use needlessly low ISO settings on their DSLRs, using ISO 100 as standard. In most situations you will gain sharpness by setting a higher ISO, because you'll get a smaller aperture, faster shutter speed, and the flash will reach further. And with newer (2008 and later) DSLRs (not compact cameras), ISO 800 does not have any noise anyway. I use 800 pretty much as default setting, and only set it lower if the light is very bright or if I want to use a slow shutter speed or a large aperture for some creative effect. (Or if image quality is very critical, for there is some difference. And even then I need to be sure I don't compromise too much on shutter speed or aperture and ruin the picture anyway.)
A smaller point Gary makes is that apparently if you set the camera to manual, you can can set the shutter speed and aperture independently and still get automatic flash exposure measure through-the-lens, I did not know that.