Tab Key

Most people know if they hit the tab key, they can hop from control to control in a program. What most don't realize is that if they hold the shift key while they tab, they can go backwards through the controls.

Sidebar:
Before you ask, Controls are the "objects" you interact (play) with in a program. Stuff like buttons, checkboxes, text boxes, lists, etc. are all controls. Basically, if you can do something with it, it's considered a control.
End Sidebar

For example, say you're filling out a form on a web page. You fill in your first name and, in all your excitement, accidentally tab right past the last name box. You can easily get back to the last name field by holding down the shift key and hitting the tab key.

So, next time you get a little wild with your tabbing, don't grab your mouse - just press your shift key.