I'm a freelance computer technician so I have no hours. I go where opportunity beckons. At least, for those I can afford the fare for. Since most clients can't really describe their computer woes in a succinct manner, I tend to lug several tools with me on these adventures.
The tools I have can be easily separated into two categories: software tools and hardware tools.
Software Troubleshooting Tools
My rule of thumb for fixing computers is always start with the software. Except for the pretty much obvious hardware problems (bashed screens, sticky keyboards and beeping POST errors), most computer problems can be fixed by tweaking on some settings or running other diagnostic software.
Hardware Troubleshooting Tools
As much as I would like to be as simple as a software problem, there are times when no amount of tweaking can save the day. The hardware parts now become "victims" to my incessant examinations. Thankfully though, most of the cases encountered almost always dealt with poor maintenance rather than the electronics going kaput. There have been special circumstances though.