Apple's Remote Desktop
If you are managing lots of Macs or need to remotely access them, Apple's Remote Desktop is a must. Effectively Apple's version of Remote Desktop Protocol (RDP), it provides a central management console which not only allows for remote observation and control, but remote software installation, machine status and lots more.
Remote Desktop's daemon is installed as part of Mac OS X 10.4 and later, so it only needs to be enabled in the Sharing system preference. You can also enable Virtual Network Computing (VNC) service if you'd rather connect with a PC VNC client.
Single-user mode+AppleJack: If you've got some Unix chops-and if you're managing Macs, they certainly give you much more leverage-then become familiar with holding down "command-S" during startup. This will put the Mac in single-user mode which halts the boot process as soon as the Unix layer is loaded-long before the GUI and all the Mac OS X frameworks load (not unlike booting in Safe Mode to the command prompt on Windows).
Single-user mode allows you get to get in and perform operations directly on the underlying operating system, such as removing corrupted preference files or obsolete system extensions which may be interfering with a full boot. An invaluable, free utility to be used in single-user mode is AppleJack, which simplifies several cleanup and maintenance operations, which can only be performed at this early stage of startup.
It's the same hardware, mostly: Keep in mind that the hardware of modern Macs is barely much different than that of PCs. If you have your doubts about a component of a user's Mac, you can absolutely swap in a compatible drive or RAM module, which would otherwise be used in a PC. SATA is SATA and DDR2 is DDR2. The same techniques apply.
Of course, these are just a few tools and techniques of the many you might need to troubleshoot a Mac, but these alone will help you through quite a few common issues your users will have. If you have questions about any of the applications I mentioned, or if you have suggestions for others you'd like to see mentioned, please drop me a line. Until next time, may you have happy Mac users in your organization.