In Finder as well as most browsers, including Safari, pressing Shift + [ will handily take you back to the previous page you were on, while Cmd + ] will take you forward, just as if you'd clicked the arrow buttons located in the toolbar.
12. Select All
Possibly the biggest timesaver of them all, pressing Cmd + A in any application will Select All. This is irrespective of whether you have a page full of text, a collection of images in iPhoto or all the files and folders in a Finder window. A superb shortcut.
13. Copy, Cut, Paste
Copying (C), cutting (X) and pasting (V) is much quicker if you master the keyboard shortcuts. But always look out for a Paste and Match Style, Cmd + Option + Shift + V, so you don't have to reformat text to match its destination.
Searching using Spotlight is obviously far quicker than navigating the file system. Cmd + [Spacebar] opens the Spotlight search box, but within Spotlight, Cmd + Enter opens the Top Hit, and Cmd + a mouse-click reveals the item in Finder.
The space bar by itself has many uses. If you're in Finder, pressing it when you have an item selected will bring up QuickView. If you're in an application and something is selected (it has a 'blue halo'), pressing the [Spacebar] will make your Mac act as if you've clicked it.
If you're in the middle of an operation (whether you're copying over some files or you're in an open or save dialog) and you change your mind, you can stop the proceedings easily. By simply pressing Cmd + . you'll put a halt to things.
17. Jump words
When you're working with text, holding down the Option key and pressing an arrow key will leap one word in that direction. Holding down Cmd will jump you right to the start or end. While, holding down Shift will select the range you've just leapt over.
This is the ultimate safety net. If something goes wrong, always hit Cmd + Z and nine times out of ten, no matter what, you'll be rescued. In some applications, there's also a Redo option to undo your Undo Typing with Cmd + Y as the shortcut.
19. Go to file path
This will work in any Open or Save dialog box and it gives you a dialog into which you can type a file path to change your current directory. You can then handily tap on the Tab key to auto-complete folder and file names, if you wish.
Save yourself the hassle of going to the web or opening yet another application by launching Dashboard, simply press F12. This is OS X's collection of widgets that perform useful tricks such as getting the weather forecast, giving you a calculator or bringing up the Dictionary.