1. Open the image you want to print. Even if your system is color-managed well, your printed picture will never look exactly the same as it does on screen. Here's a way to try out some variations to get the color you like-without wasting paper. Go to File > Automate > Picture Package.
2. Picture Package normally helps you print multiples of a single image on one page, but we'll use it for our test strip. Choose your paper size, fill in 300dpi for your resolution, and use the pull-down Layout menu to set your page for four shots. Uncheck Flatten All Layers, and click OK.
3. Now you have a layout with four images on a single page. To make it easier to work, go to Image > Rotate Canvas > 90° CW. Check out your layers: each copy of the image is on its own layer. Picture 3 is the one at top left-go to the Layers palette and click that layer to select it. Then hit M on your keyboard for the Rectangular Marquee tool, and draw a box around the top left image. Use an Adjustment Layer to Make changes. In your Layers palette, it's the half-black, half-white circle, fourth from the left in the row of icons on the bottom. Click it and choose your adjustment-I'll use Curves.
Quick TipSeem like a lot of work? Make an Action! Record steps 1-5, but make your Adjustment Layers without modifying them, so your action will work on any image. You can do the tweaking after it runs.