How do I change the background picture on my Mac?

Not an unreasonable question, actually, and the path to change your background picture is surprisingly similar on a Mac OS X system to how you'd do it on a PC running Windows XP or even Vista. Whether it's called "Settings", "Control Panels" or "System Preferences", it's a path to all the key configuration settings on your computer.

On the Mac, you'll want to go to Apple --> System Preferences..., then choose "Desktop & Screen Saver":

Now you can see all your desktop image alternatives here, ranging from dozens of pictures and images included with Mac OS X to easy access to your iPhoto library folders:

If you want to use an image of your own, here's a helpful tip too: just drag your picture file onto the "recycle" rectangle on the top left. If you don't immediately see it appear on the desktop itself, try unchecking the "Change Picture" every time interval option and it'll magically appear!