Good warming exercises

[faa2010]

What warming exercises would you recommend?

Can playing an old or easy piece be a kind of warming exercise?

How long does the warming last?

[stevebob]

I don't do any warm-up exercises before starting my practice routine, as it doesn't seem necessary.  But if the idea is to "wake up" the fingers of both hands to initiate control and coordination at the keyboard, I would recommend scales, arpeggios or a bit of Hanon.

[birba]

Argerich used to "run through" the chopin preludes to warm up. 

[stevebob]

Argerich used to "run through" the chopin preludes to warm up. 

I actually heard a different story about Argerich:  that she warmed up with Schumann's toccata.

[birba]

  She's simply amazing.