Quick rolling shots question...

I recently acquired a new 50D, and will attempt my first rolling shots this weekend. I have a Sigma 10-20mm at my disposal, which I've seen some others use for this type of application.

What is the best setting on the dial for me to be in? Any other settings that I should be aware of? Aperture, shutter speed?

I appreciate any help!

I'm on my laptop away from home, but I think my 1st link in Panning Question has something on rolling shots without rigs.
Otherwise rolling is just a version of panning. Watch your backgrounds while you're shooting.

Rick Denney's "Treatise on blur":
When is blur acceptable?

Some of my blur threads:
Dream Cruise at the Athens Coney Island

If you're on the highway, I usually set my camera to Tv (Time Value) mode and set the shutter speed to 1/60th

I'll let the camera figure out the rest and see how they are coming out after a few test shots.

1/60th going around 60mph or higher will give the background a nice blur, along with the wheels

It depends how much motion you want to capture. Rolling and panning takes a little bit of practice to get right. I personally like the blur I get with 1/40th and 1/30th of a second on shutter speeds.

I usually start at 1/70 and work my way down from there. Youre lucky you got the 10-20 so you can shoot in only 2 lanes. 1/40 usually gets a lot of motion.