Keyboard shortcuts are one of the easiest ways to increase your productivity, and many can be used across applications. Below are a few of the shortcuts I use daily; although they may seem basic to some, it amazes me how many people don't know these shortcuts. See Wikipedia's Table of Keyboard Shortcuts for even more.
|Show Desktop (min. all windows)||Win()+ D||F11|
|Select all text||Ctrl + A||Cmd + A|
|Copy selection||Ctrl + C||Cmd + C|
|Paste selection||Ctrl + V||Cmd + V|
|Undo||Ctrl + Z||Cmd + Z|
|Redo (undo the undo)||Ctrl + Y||Cmd + Y|
|Close file or window||Ctrl + W||Cmd + W|
Shortcuts keys should be held down simultaneously. The Control (Ctrl), Windows () and Command (Cmd) keys are located on the bottom row of most keyboards.