Question:

If power is out in part of the house and all the circuit breakers appear to be on, what should I do first?

Answer:

Circuit breakers can sometimes be in the “on” position, but actually they have tripped and have turned off power to the circuit.  You can quickly assess if this has happened by simply switching the breaker to “off”–then turn it back on.  If this solves the problem, good!  But an underlying question still has not been answered.  Why did the breaker trip in the first place?  For your own safety and peace of mind, check the outlets and fixtures involved for problems. If you see none–and the breaker trips again–there is some issue that should be investigated.  This is a situation when an electrician can be a valuable resource.