Instant Grabber Hand
Ever been frustrated by having to switch tools to move your image around the canvas? Here's the solution — Press the Spacebar to temporarily activate the Hand Tool. Click to move an image freely inside a canvas area that is smaller than the image. Release the Spacebar and the hand tool will revert back to the current tool you have selected

Quick Revert - The Undo Command
To undo your last image modification Press Control+Z), and repeat the shortcut to undo the undo. Toggling back and forth like this is a good technique to review the before and after effects of a one-step change to an image, like dodge or burn
NOTE: Photoshop has ONE undo level. Ctrl Z will revert / repeat.
To go back further (more undo's) Press
Ctrl+Alt+Z to select history movements. In this manner, you can undo back to any stage, although difficult to hold hand around those keys, but faster than individual selecting history components.

The Move Tool & The Arrow Keys
Get in the habit of calling up the Move Tool with the keyboard shortcut, which is the letter V. Also, once the Move Tool is active you can use your Keyboard Arrow Keys to nudge a layer or selection in 1 pixel increments. To speed things up, Press Shift along with an arrow key to nudge in 10 pixel increments.
Important Tip:  Always stay in Move Tool Mode, safer between steps of thoughts of creativity. Today, all our graphic artists have developed the habit of immediately switching tools to sit idle in the Move Tool, less errors..