First, for those new to the operating system, here’s a quick overview on the “standard” methods of repositioning the OS X Dock. The first and most involved method is to head to System Preferences > Dock. Here, you can make changes to the way that the Dock works and looks, but what we’re interested in is the “Position on Screen” options in the middle of the Preferences window.
Simply click one of the radio buttons to move the Dock to the left, right, or bottom of your screen.
A quick note here for those using multiple displays: if you have additional monitors to the left or right of your primary display, selecting the “left” or “right” positions will move the Dock all the way to the left- or right-most edge of your last display on that side. For example, if you have an iMac as your primary display and a Cinema Display positioned to the left of iMac’s screen, if you choose to position the Dock on the left, it will move all the way to the left edge of the Cinema Display, and not the left edge of your iMac display.
Another way to access much of the same functionality that's found in System Preferences is via a handy contextual menu in the Dock itself. First, find the thin line that separates your Dock applications from your user folders and minimized apps; it’s usually on the right end of the Dock. Then just right-click (or Control-click) on that dividing line to reveal a menu with the most common Dock options, including Hiding, Magnification, Minimize Effect, and, for our purposes, Position.
This method is notably faster than going to the Dock preference pane in System Preferences, but there’s an even faster method that we haven’t touched on yet: the Shift key. That’s right, it’s usually the Option key that gets all the love in OS X for its hidden functionality, but today the Shift key takes the spotlight.
To use this method, find that dividing line in the Dock again, and this time press and hold the Shift key on your keyboard and Left-Click (not right-click like the previous methods) on the Dock divider.
Keep holding both the left mouse button and the Shift key and then drag your mouse or trackpad cursor to the right or left of your screen. As you approach the edges of your Mac’s display, you’ll see the Dock jump to the corresponding side. When you want to move it again, just repeat the steps to reposition the Dock back to the bottom, or to the opposite side of your display.
This method is not only faster than either of the first two methods, but it also makes it easy to move the Dock out of the way when you need to for a specific task — for example, to view the maximum height of a website, or enlarge the working space while editing photos in Lightroom — but then restore it to its original position when you’re done.
Check out the video embedded above for a visual demonstration of these methods.