[jamesbritt]

Thumbs up on Screenflow. It does quite a bit for $99. I especially like how easy it is to swap in alternate takes of things.

I've been using it to develop live presentations with slides, and was very helpful in working out a talk for Ignite Phoenix, where timing is extra crucial.

I tend to write down some notes, then do a recording more or less ad lib, see how much I screwed up and flubbed things, and gradual get a feel for what phrasing feels most natural, what steps are needed, what I have to explain.

The end result is a sort of pre-recording of your talk, which you can watch as an aid to practising and getting the whole thing into our head.

Also, good point on keeping screencasts short. I hate having to jump around in some 20-minute recording trying to find where one or another item was explained. Better to break things down to a set of tighter presentations.