Originally posted by Terrelian:Well, it's a bit trickier than you'd think. By default, the screenshot key is mapped to F12 - so on a PC, you'd just press the F12 key and a screenshot would be taken. On a Mac, it's not so simple: the function keys all have different purposes. Pressing the F12 doesn't actually register in the system as an "F12 Press" - it boosts the volume instead. To ACTUALLY trigger F12, you have hold the little 'fn' key and press F12 at the same time. (The "fn" key is typically found in the bottom left corner of your keyboard.)Solved, right? WRONG. F12 is mapped to bring up the dashboard by default.So, you have two options. You can go in to your system preferences, go to the "keyboard" section, click on the "Shortcuts" option from the four presented, then select "Mission control" from the list on the left. See the thing that says "Show Dashboard"? Either uncheck the box next to it to disable it, or you could click the "F12" to the right of "Show Dashboard" and map a different key combination to it - thus freeing up the fn+F12 combo to take screenshots.The other method is slightly more intuitive. Open up the Steam Client on your Mac. From the Menu bar (the one that has the Apple icon, then "Steam", then "Account" then "View", etc, etc), click "Steam", then select "Preferences" from the list of options. From the resulting list of preferences, select "In-Game" (It's smack in the middle of the seven options). Now, on the right side of the box is "Screenshot shortcut keys", which will currently be F12 - change it to any one key or any combination of keys that you like. (If you choose a combination of keys, you'll have to press them all at once to take a screenshot.)I apologize if this seems rather wordy. After years of troubleshooting for my grandmother, I figure it's best to be as unambiguous as possible.