Here are some useful photoshop shortcuts.

H (Hand Tool) — When zoomed in to a portion of your photo, this command brings up the hand tool which allows for quick panning. Also, if the hand tool is active and you hold down the Ctrl key, you can zoom in without changing to the zoom tool. Likewise, if you hold down the Alt key, you can zoom out without changing tools.

Z (Zoom Tool) — This command just brings up the zoom tool, which allows you to zoom in. Like with the hand tool, if you hold down the Alt key, it temporarily switches to the zoom out mode.

Ctrl + 0 (Fit on Screen) — This is a quick-and-dirty command to get the entire photo in front of your eyes. That’s Ctrl + zero, not the letter “O”.

B (Brush Tool) — The brush is an extremely useful tool when working with masks, and I’m constantly using this command along with the hand and zoom tools.

Ctrl + Z (Undo) — Very useful for the little mistakes we all make.

Tab (Hide/Show Palettes) — Hiding the palettes gives you a little more working room, thus decreasing your need to pan and zoom while editing.

Space bar - Press and hold the space bar will temporary bring out the Hand tool, allow for panning.

More shortcuts
G - Paint Bucket
D - Reset foreground and background colour to default, that’s black and white.
X - Swap current foreground colour with background colour and vice versa.