This is the best resource I have ever come across regarding piano practising techniques (good resources describing how best to practise are to my knowledge, quite rare).
It’s not a series of boring technical exercises and it’s not airy fairy new-age musician mumbo jumbo talk. It discusses learning techniques with a fairly well reasoned scientific approach. The book offers short cut methods to learning difficult passages and educates readers so they can avoid poor practise techniques that will stall or even reverse their progress.
These ideas can easily be applied to other instruments.
Heres’ the link: http://www.sinerj.org/~loyer/PianoBook/piano-practice-a4-10pt.pdf
I have just discovered the above link no longer works. 😦
I’m pretty sure this site is the new version of the above material, but I’m going to check: