Change of default behaviour when connecting to external display: mirror mode Some OS generations back the default behavior when a new display was attached was that the screen was mirrored. 

I would like to get this behavior back since without it I have to fiddle with the system settings every time I want to give a presentation, since the projector I am connecting with is new to the OS and I have to set up everything.

So question: Is there a plist or something that I can change once and for all?
Just press ⌘ + F1 after connecting the display to your Mac and your screen will mirror.

ps. you might have to press fn as well. This depends on how you've set up your F-keys.