Deduce from your observations of the symptoms what the problem might be.
This is where the magic and art apply to problem solving. The process of deducing from your observations of the problem and your knowledge and past experience is where art, religion and magic mix with science to produce inspiration, intuition, or some other mystical mental process that provides some clue to the root cause of the problem.
In some cases this is a fairly easy process. You can see an error code and look up its meaning from the sources available to you. You can then apply the vast knowledge you have gained by reading the DataBooks® For Linux and the documentation provided with Linux to deduce — the magic part — the cause of the problem. In other cases it can be a very difficult part of the problem determination process.
It helps to remember that the symptom is not the problem. The problem causes the symptom. You want to fix the true problem not just the symptom.