First of all:
A lot of good info in this thread.
Second:
Forgive me if I repeat a lot of what has already been written.
I will try to go through it with a slightly different take.
Definitions.. just so we are clear:
A cascade is descending by definition. Having said that, there are varieties.
Stationary cascade (puddle)
Rising cascade (fountain)
NB - do not use the term "Up The Fountain", otherwise mr. zipman will seek you out wherever you are and beat you with whatever kite you happen to be flying at the time. I will pay him to do it. And pay his air fare. Just don't.

Once you learn the basic drill you will, through very simple adjustments, be able to do any of the Three types so, for now, just put it out of your mind.
Here's what it looks like:
>-<
Start off nose facing right.
Then you are going to put the kite into a pancake nose away.
Then you are going to stand the kite back up with the nose facing left.
Then repeat, etc..
One of the ways to practice this is to start in a tip stand (yes, that's right on the ground), lay the kite belly down with the nose directly away from you, and then pop the kite back up onto the opposite tip.
This will not get you the perfect cascade. It probably wont even look very good. What it will do is give you an idea of the range of motion the particular kite you fly needs in order to complete a cascade.
Just to be clear: even if it looks like crap; even if you only get part way through, it will help you to get in the ball park as far as how much slack to give for the pancake, how big an input is needed to stand the kite back up, etc.. oh just humor me. It'll help even if you only do it a couple of times. Mainly it saves you having to worry about flying the kite while you are getting an idea..
Kite in the air:
Nose facing right - pop the upper wing with your left hand - give slack with both hands to lay the kite down in the pancake nose away - pop the right hand and take up slack with the left hand to stand the kite back up facing left - pop the RIGHT hand and give slack with both hands to lay the kite back down in the pancake - pop the left hand and take up slack with the right hand to stand the kite back up facing right - pop the LEFT hand and give slack with both hands to lay the kite back into the pancake position...
did you get that?
>Left - Right < RIGHT - Left > LEFT - Right < RIGHT - Left > LEFT -
Some blather on slack:
You often hear the Phrase "fly the lines not the kite" and it's good advice as far as it goes. The problem with "fly the lines not the kite" is it doesn't, in fact, take into account the kite you are flying.
The kite you are flying has everything to do with how you go about "flying the lines".
One of the biggest failure points for tricks in general is not observing what the kite needs in order to complete a move. They are all different. Some need to be tricked slow, some fast. Some need a lot of slack, some don't. Figure it out.
Take it easy. Relax. Observe what happens. Don't be in a rush to give the next input. Let the move develop. If it over rotates, "over-develops", well then fine. Now you know. "Oops, that went too far" You will never know what is too far unless you go there. Go there, then back off.
A long winded way of saying your kite may not need slack with both hands for the pancake, it may not need any extra slack at all, it may develop tons of slack on its very own... and the same with the other elements of the cascade. IOW, it will vary.
And a long winded way of saying you need to move or not move as dictated by the wind, the kite you are flying, how tall you are, how short you are, your strengths and weaknesses as a flier... it all figures in.
A word or Two on the variations:
Cascade.. To descend, it may only require that you move in on the kite, or cascade more slowly. A generally sure fire descent can be had by pancaking with the nose down to some degree.
Puddle.. Again movement can be your friend, when going for that stationary cascade, but so can making sure you are going truly flat in the pancake.
Fountain.. Rising cascades work best if you allow the nose to go high in the pancake. Also, rhythm and emphasis, on the inputs, different for different kites, will help you to get the cascade to rise.
Maybe a bit over the top.. anyway.
HTH