I've used a simple subset of 3 rules:
1) Nr - maintain. Because rotor rpm is your life. Sometimes this means lower collective, sometimes it means raise.
2) Hi/Hi bad - low/low bad. Distillation of Nick's description to decide whether the high or low engine is the bad one. You can always tell by Nr.
3) No fast hands in the cockpit. Regardless of rule 2, deliberate and consult with the other pilot before moving ANYTHING other than a primary flight control.