Problems are identified by asking questions - lots of them!
Say for example an employee at work is consistently under performing, but company records show that this individual has received several training courses over the past year.
You could begin to ask: Did the individual actually attend the training courses?
Did he/she pass the assessments for the course? Did these particular training courses actually have some form of assessment?
Once you've identified what is causing the problems you're sitting with you can begin to deal with them. Problems should be tracked and you should request feedback on the issues until they are fully resolved.
By being persistent with issues like these you create a more functional work environment where problems are addressed before they escalate into far more serious ones.