Ongoing list of Tips and Tricks by Operating System
Lock your computer before leaving your desk
This is something you should do EVERY time you leave your computer (this is good practice even at home; especially if you have kids or pets).
Windows: Windows Key + L
macOS: Control + Command + Q
Paste from your clipboard history
Remember a few copies ago when you copied someone's name and you want to paste it again but you already copied something else that is in the clipboard? No worries, paste from the clipboard history.
Windows: Windows + V
macOS: You will have to use a third party like Clipy to get this functionality.
Take a screenshot of a section of your screen and save to the clipboard
Windows: Windows + Shift + S
macOS: Shift + Command + 4 (Note: this saves the screenshot to the desktop)
Take advanced screenshots (gif, screencasts, annotations, arrows, etc)