1. Use the Reset Button. When you are in a Photoshop dialog (for example, the Image… dialog) you can press the Alt key on your keyboard (Option on the Mac) and the Cancel button will change to a Reset button and you can change back to whatever settings you altered.
2. Press Alt / Option to turn Brush into Eyedropper. When you are using the Brush tool, you can hold down the Alt key and the cursor will become an eyedropper allowing you to make quick changes to your paint color.
3. Using the Eyedropper outside of Photoshop. Did you know that the eyedropper tool in Photoshop works outside of Photoshop? Yeah, it does. To do it: choose the eyedropper tool and click inside your image. Then drag anywhere on your screen to select a color from anything visible on your screen. More details are at creativebits.
4. Use the Alignment Buttons. If you have multiple objects and you want to line them up you can easily do so by linking them together and using any one of the alignment buttons that appear when you have the move tool selected. This tip is great for lining up multiple text strings or shapes.
5. You can change the brush size by pressing the bracket keys repeatedly. This one is handy for quickly changing your brush size. Simply pressing either ] or [ and it will adjust the brush size by 10 units. Thanks to Ward at Mister Shape for this tip.
6. Pressing the shift key constrains proportions when you resize objects. Simple yet obviously not everybody knows this one. If you don’t hold shift, it stretches. Honestly, I think Adobe products should automatically hold proportions.
7. Using the erase or pen tool, you can press erase once and then holding down the shift key press somewhere else to draw a straight line: Simple yet effective and works with other tools like the pen tool.
8. Shift + Backspace fills a selection. Yup, another super-simple one. It’s the same as going to Edit… Fill…
9. Set your Units of Measurement to pixels. If your artwork is destined for on screen display you should set your Rulers to display units as pixels (it can display inches or whatever unit of measurement that you might want). Often times when I receive someone elses Photoshop file that has guides in it, I find the guides are not snapped to the edge of the pixel. This is because the guide was placed when the unit of measurement was something other than pixels.
10. Use the sharpen tool on photos. Especially if your photo is destined for web use (or email) and you just resized a big picture to small dimensions. It makes your photos crisp and makes everything and everybody clear. I wrote more about this in April.