How do I tell OS X to always mirror displays when I plug them in? I plug the same external HDMI monitor in every day, and each time, I have to manually switch from external to mirrored mode. It's minor, but annoying.

Is there a way to tell OS X to default to mirror mode whenever I plug in a monitor? I looked in System Preferences -&gt; Displays, but I couldn't find such an option.
You didn't say what version of OS X you are using. Yosemite remembers your settings by default so just set it once.