Circuit ID is always a timely topic; we've discussed it many times.
Still, even the best marked panel leaves something to be desired. When circumstances allow, I like to mark the cover plate of each device.
Code issues aside, It is my opinion that you should be able to quiclky, easily, and accurately find the corrrect breaker with a minimum of fuss.
This is not possible, however, in a 'code minimum' installation. Circuit identification depends upon the circuits being laid out in a manner that makes sense to the occupant- which is usually somewhat different from the absolute cheapest way to wire a home.
