Moving your hand from your keyboard to your mouse is inefficient computing. Keystrokes, such as Ctrl-C to copy and Ctrl-V to paste, save you time and repetitive strain from mousing.
One of my favorite key strokes that few people use is Alt-Tab. When you click Alt-Tab once it takes you back to the window you were using last. So much faster than a mouse click. If you hold Alt and then press tab once it will show all your recent windows. You can keep holding Alt and tab, tab, tab your way to the window you want.
Try it!
What is your favorite keystroke.