The following are general recommendations as summarized by Boeing in 2011. Each operator's flight operations manuals may include more specific instructions.
Flight conditions permitting, reduce thrust to idle immediately; turn the autothrottles off.
Exit the ash cloud as quickly as possible; a 180-degree turn out of the ash cloud, using a descending turn, may be the quickest exit strategy.
Turn on the engine and wing anti-ice devices.
Turn on all air-conditioning packs.
If possible, start the auxiliary power unit.
If volcanic ash reaches the flight deck, the crew may need to use oxygen.
Turn on the continuous ignition.
Monitor the engine exhaust gas temperature.
Fly the aircraft by monitoring air speed and pitch attitude.
The Air Line Pilots Association's Safety Department further recommends:
Do not attempt to climb out of the ash cloud.
Perform engine restart, if necessary.