avoidance of excessive wrist movement/rotation (which slows things down)
It's interesting to see the different schools of thought around this. The last recital I went to, the pianist had a very rigid, fixed wrist, yet his RH ascensions were brilliantly played at incredible speeds. On the other hand, I've seen similar results with the "wrist circle" idea.
Wrist movement mainly becomes important with octaves. With single-note scales you can get away with nearly any wrist movement strategy.
Definitely not what my (great) teacher would say.
Having the arms "hanging" relaxed from the back and being able to articulate clearly and with a lot of sound, a lot of pressure each notes is what she's teaching to me. I used to play with a rather fixed wrist... well :
1) you can't really play loud
2) the sound isn't great
3) it hurts (if it's not now, it'll be later)
Of course a supple wirst does not mean you do not need a terrific finger technique. You need both, they're complementary !
About scales, the method of speeding up with relatively large increments and then goind back to (sometimes very) slow to "clean" works very well for me. After a while my mind has gotten used to it and it's a very efficient way to work - moreover it forces you to concentrates, you can never really play mechanically doing that.
Speaking of that, do not forget the ears.
The ears are ultimately what will decide between a sloppy scale and perfect one with a good articulation and a good sound. It's never productive to be strictly mechanical. IMHO it's good to always remember that, at least it is for me.
For instance, listening to the left hand better in a scale can solve coordination problems. etc.
