Customize Your Workspace
When working on projects it helps to have the tools you use most to hand where you can quickly access them when needed. Why not close the panels you don't use and display the panels you do use. Not only will this maximise your workflow it will also free up some space within your work area. You can also setup different workspaces for different tasks, whether it be 3D work or painting. Just choose "Window > Workspace > New Workspace", name it and arrange your panels as desired.
Closing And Creating Documents
You can close multiple documents quickly by pressing "Ctrl + F4" to close the active document. Hold down "Ctrl + Shift + F4" to close all open documents. If you have multiple changes you’d like to discard, check the Apply to All tick box when choosing Don’t Save to avoid having to confirm each document as it is closed. Quickly create new documents with the shortcut "Ctrl + N".
Work With Actions On Repetitive Tasks
If you need to perform a series of steps more than a couple of times, you will almost certainly save time by recording an action. Open the Actions panel by going to "Window > Actions" or "Alt + F9" and click the Record button at the bottom of the panel. Perform your steps, then click Stop. Photoshop will invite you to name your action, then simply select it and click the Play button to repeat the steps.
Quickly zoom to 100% with "Ctrl + 1" or quickly fit to screen with "Ctrl + 0".
Less Distractions In Full Screen Mode
Toggle between different full screen modes with the shortcut "F" and the "Tab" key.
Centering objects inside of an element or centering an element inside of the canvas is made easy with photoshops alignment tools, see this quick guide for a more in depth look.
Turn On Smart Guides
Smart Guides are a great way to quickly align elements without having to resort to manual guides. Enable them by choosing "View > Show > Smart Guides", and as you move layers around within the canvas Photoshop will automatically show and snap to adjacent objects, making it very easy to get a perfect alignment.
Selecting Layers Quickly
If your PSD file contains multiple layers, so many you struggling to find a particular layer without hiding and unhiding other layers. Then simply select the "Move Tool" shortcut key "V" then select between "Groups" or "Layers" from the drop down box in the tool bar. Now select the element within the canvas and the layer is simply automatically selected for you.
Moving Around The Canvas When Zoomed In
Cutting out an image for example you're zoomed in 1600% with the polygonal marquee tool. You can't navigate with the scroll bars incase you risk losing the selection, you slide your mouse to edge of the screen but the screen moves quickly out of view. Sound familiar? try holding down the "Spacebar" the click and drag with the mouse.
Hiding And Showing Layers
You can quickly hide and show multiple layers by simply clicking and dragging the mouse over the layers visibility option.
Changing Brushes Sizes
Change brush sizes on the fly by using the brackets shortcut "[” decreases the brush size and “]" increases the brush size.
Turn On Brush Outline
When using the brush tool its handy to sometimes see the actual brush, you can of course permanently turn this option on in the preferences but why not just toggle it on and off by using the "Caps Lock" key.
Duplicate layers quickly and easily by holding down the "Alt Key" in conjunction with an arrow key or a mouse click and drag motion.
Improve The Layers Panel
Select the little black arrow in the corner of the layers window and select "Panel Options". Change the thumbnail size to large then crop the thumbnail contents to the "Layer Bounds" You can also turn off the "Expand Option" when adding layer styles and stop photoshop from adding the word "Copy" after every duplicated layer.