Some good information can be had by searching some YouTube videos.

Here was a simple search: http://www.youtube.com/results?searc...rch_type=&aq=f
If you are looking for a more specific cast you can search under that cast.

There are some good DVDs available and many libraries even have rentals on these for free.

Here is a link of demo casts from the FFF or Federation of Fly Fishers that their instructors can view to pass their minimum performance tests: http://www.virtualflycasting.com/certexam.htm

The best way is personal instruction from a qualified instructor. If you go to the FFF site, you can find an instructor in your area: http://www.fedflyfishers.org/Default.aspx?tabid=4465

Good luck, Rick