Once you have identified the symptoms, you can begin to formulate some of the potential causes of those symptoms.
Identifying the Affected Area
Some computer problems are isolated to a single user in a single location; others affect several thousand users spanning multiple locations. Establishing the affected area is an important part of the troubleshooting process, and it will often dictate the strategies you use in resolving the problem.
Problems that affect many users are often connectivity issues that disable access for many users. Such problems can often be isolated to wiring closets, network devices, and server rooms. The troubleshooting process for problems that are isolated to a single user will often begin and end at that user's workstation. The trail might indeed lead you to the wiring closet or server, but that is not likely where the troubleshooting process would begin. Understanding who is affected by a problem can provide you with the first clues about where the problem exists.
Establishing What Has Changed
Whether there is a problem with a workstation's access to a database or an entire network, keep in mind that they were working at some point. Although many claim that the "computer just stopped working," it is unlikely. Far more likely is that there have been changes to the system or the network that caused the problem.
Look for newly installed applications, applied patches or updates, new hardware, a physical move of the computer, or a new username and password. Establishing any recent changes to a system will often lead you in the right direction to isolate and troubleshoot a problem.
Selecting the Most Probable Cause of the Problem
There can be many different causes for a single problem on a network, but with appropriate information gathering, it is possible to eliminate many of them. When looking for a probable cause, it is often best to look at the easiest solution first and then work from there. Even in the most complex of network designs, the easiest solution is often the right one. For instance, if a single user cannot log on to a network, it is best to confirm network settings before replacing the NIC. Remember, though, that at this point, you are only trying to determine the most probable cause, and your first guess might, in fact, be incorrect. It might take a few tries to determine the correct cause of the problem.