I was going to go to sleep, when another support called rolled in (PS If the client reads this, take no offense. It happens all the time but this skill I'm talking about is critical and should be practiced more often by everyone). It appears the art of troubleshooting has become more of a shotgun approach than a fine scalpel to perform the necessary task. Here is how I approach troubleshooting.
Walk the Path.
Very simple, yet very powerful. I was taught this at my first job working the campus help desk at UC Davis (my mentor's name was Henry but I forgot his last name). Walk the Path is very "Grab the butterfly from my hand", but it works. Very well I might add and it has saved me (and other consultants I've mentored) numerous times.
So what does it mean... Simple. Start doing the task like a computer and start at the first task. Based on the result, go the next process/task. Based on the result, go the next process/task. Repeat until enough information has been gathered to solve the problem, or make educated changes based on the new information (or at least eliminate that its your problem so you can assign it to someone else ;-) ).
Without this approach, you shooting blindy at the problem and though you many know the programs inside and out... it may take you longer to resolve the problem because you overlooked something or made an assumption that didn't hold true.
As an example when troubleshooting SMTP, telnet IPAddress 25 is the first thing to try (This will tell you the SMTP service is working). If you connect, telnet DNSName 25 (This will tell you the service is working and DNS is correct). It it works, then issue the HELO or EHLO command, etc, until I either solve the problem or I come to the next step based on the failure or success of the prior step.
Another example. Client complains "Citrix is not working". After explaining that Citrix is the company name and ensuring them that Citrix employees work real hard. I walk the path of Presentation Server from the inside of the network, can I ping the Presentation Server? Then can I telnet IPAddress 1494 or telnet IPAddress 2598? Can I telnet IPAddress 3398 to verify Terminal Services is working? What about a remote file share (\\IPAddress) or a Manage My Computer remotely to the IPAddress? All of this information leads me down a path toward solving the problem.
Now, it really helps if you understand fully what the programs/services are doing, the order in which they communicate and the ports/protocols in use... but you still can Walk the Path knowing at least the first process or task to perform... Then googling (God bless Google!) the rest of the steps in the communication flow.
Now go take your first step and Walk the Path for me. Let me know how it goes.