Mac tricks you don't probably know

1. Shift the screenshot selection area: OS X allows to take a screenshot of a selected area of the screen with CTRL/SHIFT/4. If you need to select an area located slightly above or below your starting point, press SPACEBAR without releasing your mouse to shift the selection where you need it.
2. Move selected files to a new folder with a click: Select the files you want moved by pressing down CMD while clicking them, then right-click your selection and choose New folder with selection. Afterwards your files will be automatically moved to a new folder that will get the default name New Folder with items.
3. Put your Mac to Sleep with a keyboard shortcut: You can put your Mac to sleep by using the combination ALT (aka Option)/CMD/EJECT (⌥ ⌘ ⏏). 
4. Delete Trash on the fly: You can delete the Trash with CMD/SHIFT/BACKSPACE and clicking Empty Trash when a confirmation message pops up. If you want to empty the Trash right away, you can utilize CMD/SHIFT/ALT/BACKSPACE and no confirmation message will be displayed.
5. Freaky fast logout: Need to log out real quick? No biggie, the key combination ALT/SHIFT/CMD/Q deals with that for you.