go to their video section and download the video's of larry. you can get a good idea about how you are supposed to edge by watching him...I think they have some vid's of other people doing stuff off the lines too.
But as you'll see you have to have a really good edge and push it hard (in the vid his butt is just about in the water) then kind of just stand up/scoop your feet behind you.
I've in the process of learning this and was told it's better to learn backrolls first. And for that as you are getting off your edge you just pretty much look up and away (in the direction of your lead shoulder).
One of the cable Pros (sorry Dave didn't get your last name) was helping me out at OWC the other day and that is basically what he was telling me.