...there was a video on cboater.com
you can also initiate by a cross deck draw. Give hard edge to your offside and you'll go vertical. This also works to get into a bow stall.
One your bow is going down, you rotate you body to the off side again, which throws your stern down. I think this is an offside cartwheel. (stern onside edge smashes into the water first)
Onside, I do it with the double pump. The key is, as Judd said TO ALWAYS BE AHEAD OF YOUR BOAT. Otherwise, the cartwheel kind of fades out.
So, double pump, then rotate onside shoulder to stern and look at the stern. That smashes the offside stern edge into the water first. Once you face the stars, rotate your onside shoulder to the stern again. Imagine to place the paddel behind you, flat on the waters surface (which needs quite agressive rotation).
The most important thing, from my experience, is the edge transition. This is best learned by the excercise Judd talked about. Sit in the boat, start rotating your onside shoulder to the stern and give an offside edge. Then rotate your onside shoulder to the bow and give an onside edge. A slight weightshift foreward and backward helps. When you do that the right way, you can easily handcartwheel your boat.
Some boats need to be rocked to initiate the ends to dive...
My Delirious cartwheels by itself, no paddle needed (sometimes, in drops, it seems even no paddler is needed...)
To work on the bow stall, I find it very useful to handpaddle first. this way, it is easier to not fall over to the off side (since you have two hands to balance on each side---I KNOW this is not strictly C1 since I use 2 hands
)
Chris Joose has a cool article on Cartwheels on his page.
Hope that helps a bit, Jan