Thrust levers:

at idle (if possible of course

otherwise as slow as possible )
Autothrottle ( if engaged ):

disconnect
Engine start switches:

Put the ignition on -> continuously igniting
Pack switches:

at full power

(bleed system fully open)
Wing anti-ice:

on (cause bleed system full on)
Engine anti-ice:

on (cause bleed system full on)
APU ( if available ):

starting APU when cleared of ash cloud
And a final advisory, if ever you encounter an ash cloud try to come out of it asap (even by doing a 180° turn) and don't try to fly over it.
Chris