Everyone knows a handful of keystroke shortcuts in Adobe Photoshop CS4, such as CMD+Z for Undo, and copy/paste operations, but not too many people realize that just about every command in Photoshop can be assigned a quick keystroke timesaver.

Don't get me wrong: Actions and workflow automations are amazing timesesavers. But there are many a project where it is necessary to individually "touch" and manually perform the same operation repeatedly, when it just isn't possible to automate or script it and pop out for a coffee while Bridge, Photoshop, or Lightroom chugs away.
And in these cases, the ability to quickly create a keyboard shortcut in Adobe Photoshop CS4 can be a serious time and motion-saver. For example, a project I am currently working on required over 120 copy>paste>position and scale operations.
Almost every computer user knows CMD+C followed by CMD+V will copy and paste the selection, but the default set of CS4's keyboard shortcuts don't have one for Edit>Transform>Scale. But the great thing is, you can add your own keyboard shortcuts for just about every menu-driven operation (and editing tools, too!) available, including any third-party filters you may have installed.
Take a look at this first screenshot: There's an active marquee selection on the image, and we want to scale this up or down. Now, if you are only doing this once in a blue moon, there's no real need for a keyboard shortcut. But imagine having to go through the dropdown menu more than 100 times in a recursive workflow!

Edit>Keyboard Shortcuts (or CMD+Option+Shift+K) will launch the Keyboard Shortcuts window. From here, you can assign or reassign keystrokes for just about anything and everything in Adobe Photoshop CS4–including your customized plug-ins such as Nik Sharpener or Silver Efex Pro. Here I assigned CMD+E to Edit>Transform>Scale. Originally, this was assigned to Layers>Merge Layers, and I'm going to switch it back to that once I'm done with this project. There's a ton of pre-assigned keystroke commands in Photoshop CS4 and odds are there's a bunch of commands you'll rarely use, but others may use every day. I chose to temporarily change CMD+E into my Scale shortcut because the E key is right next to W on the keyboard, and CMD+W to close the current image was the step right before going into the destination image and scaling the copied pixels.

Now, check out the Image>Transform>Scale menu item: there's our keystroke shortcut!

Now check out the next screenshot. Here we've decided to assign CMD+F (F meaning "Flip" was my thinking) to the Image>Transform>Rotate 180º command. But this keystroke combo is currently assigned to Filter>Last Filter. So here we can choose to assign CMD+F to Rotate 180º and then reassign Filter>Last Filter, or come up with a new combo for 180º rotation. Do whatever makes the most sense for you and your workflow.

For example, I've made CMD+COMMA and CMD+/ my speed buttons to switch bit depths and launch Photoshop CS4's Tone Map window when I've got a 32-bit HDR image open. CMD+COMMA isn't a conflict, but CMD+/ launches the Help box. I use Help a heck of a lot less than I use the Tone Map processes, so this is a swap-out that makes a lot of sense for me and my workflow. Do what works for you. Yesterday's project's workflow involved repeating the same steps manually more than 120 times. And it would have taken a lot more time and movement to accomplish, were it not for customized keystrokes.

Click the summarize button on the Keyboard Shortcuts dialogue box to save your modified set of keystrokes as an HTML page taht you can then print out from any browser. And attentive readers will also note the Save icon in the shortcuts window: you can save and load your keystrokes into all your installed versions of Photoshop CS4.

Here's another trick to streamline your Photoshop workflow
Look at the other tab on the Keyboard Shortcuts window: Menus. From here you can do a couple of things to help yourself out when you're working from the dropdowns: Turn off commands you never use, for example, see that I've hidden "Check in..." since I'm not working in a networked asset environment. But I do rely on "Open Recent" a lot, so I've color coded it green, just to make it pop from the list a little more.

Hopefully, these quick simple tips will help you maximize your speed while minimizing your time per image in your Photoshop CS4 workflow. My thinking is: any time you can minimize mouse movement to make it happen, you should!