Awesome thread,
it’s great to have another staff juggler out there and also online!
Tommy (irinus) and meg have both described the flat cascade variations perfectly, if you are planning to juggle staffs with fire i think the flat plain is best because of where you hold the staffs,
if you aren't then like the cat says the wheel plane has lots of potential, and is also easier to learn.
personally i think the french cascade is much nicer than antti's cascade as it makes the direction change of each catch/throw look great.
the shower wont nessisarliy destroy your shoulder (ask Josh, Tim chown, Imakakode, Koothor,) it destroyed mine because i was an idiot, didn't warm up, didn't listen to my body, and did lots of other silly things!
i totally agree with meg however that you should learn the shower in both directions as this will definitely be better for your body and also open up more avenues for future tricks. it’s the same throw as the revrse flat reverse cascade for example
if you want to learn the shower my strong recommendation is to work on the two staff shower until you can do it in all of the variations below
small(height) and fast/slow spins
medium(height) and fast/slow spins
big(height) and fast/slow spins
i would also work on
2-ups from a small shower,
then continuous 2-ups from a small shower,
then continuous 2-ups from a start,
then the above with a hand clap where the third staff will go!!!!!!
another tip for when you get to three staffs is to hold the spare staffs in your catching hand(see daylight video below) this will put less strain on your throwing shoulder, it makes starting slightly harder but means you never have more than one staff in your throwing hand.
(its your throwing shoulder that has the most potential to get hurt/injured)
also regarding the shower there are two main variations, there is the RHD shower which involves spinning the staff during the pass from catching hand to throwing hand(meg & tommy please help describe this better ta, x).when done properly the rhd shower is gorgeous but very hard to do.
the other method which is my version(as far as I'm aware) involves passing the staff over from caught hand to to throwing hand without any spins similar to the usual club juggling style for a flat shower.
This video shows both variations of the shower with two staffs fairly well,
http://video.google.com/videoplay?docid=-1123519965984155103&ei=BTnRSYjmHdSI-Aaoy8XSAg&q=tim+marston
Personally i would recommend learning my version first as it is easier to learn, once you have good control of the juggling you can try to add the RHD spins , but this makes life a lots harder.
Finally, my website video page has 3sexy (expensive!) fire vids,
My solo video has the French cascade with fire, you should be able to see the forced figure of 8, and the others have some of my and Tim clown

trying to do the cascade in time and failing(close but yet so far!!!)
http://www.jugglinginferno.com/video.aspone more fire video with 2&3staff showers and some doubles footwork, there is lots of potential to convert 3 club footwork patterns to staffs which i am currently working on...watch this space
http://www.youtube.com/watch?v=SeKKOyAKH8wGood luck dude