Just a quick list of useful shortcut available with Photoshop. There is a great many more but I think those are what will really save me time.

Basics shortcut like tool selection are easy to get, just over your mouse on a tool, the shortcut will appear in a tool-tip along with the name of the tool.

Quick shortcut list:

• ctrl+J / cmd+J : Duplicate layer
• ctrl+E / cmd+E : Merge layers
• ctrl+G / cmd+G : Group layers
• ctrl+i / cmd+i : Open image size dialog
• ctrl+C / cmd+C : Open canvas size dialog
• [ : Decrease brush size
• ] : Increase brush size
• ctrl+T / cmd+T : Transform, them right click on the layer to get the transform menu
• D : reset foreground and background color to black and white
• X : swap foreground and background color
• ctrl+N / cmd+N : New document
• ctrl+alt+Z / cmd+alt+Z : move backward in history
• ctrl+shift+alt+S / ctrl+shift+alt+S : open save for web dialog
• ctrl+Tab / cmd+Tab : switch to next opened document

These are the one I use the most. If you have some other that you use all the time and are not in the list don’t hesitate to share with us in the comment section.