Whichever decision making model you use, always start from a strong position, therefore, in the short term I start with by:
Flying the aircraft - Agreeing the failure - Performing the memory items, if any - Executing the Abnormal Checklist - Running the Normal Checklist, if any.
You now have safe(ish) aircraft. Pick a model to help you make the next decision.
What I have been taught to do is gather information - MEL, AOM's, Circuit Breakers, Fuel on board, Weather, Performance Limitations, Cabin Crew, ATC, Company, NOTAMS and so on.
Now decide. Then...
Set up FMS, Inform ATC (not forgetting to let them know of any special requirements) then execute plan.
Now inform Cabin Crew (NITS or something similar), Company, Passengers etc. Maybe a quick recap to confirm that you are being sensible.