With the original image open, click the "
Create new fill or new adjustment layer" icon in the Layers palette and select
Curves. From the Channel drop-down box, select the
Red channel and drag the top right of the curve a little to the left. Then drag a couple of points on the curve so that it forms a very gentle S — darkening the shadows and brightening the Red channel's highlights.
TIP: To save your curve to a file on your hard drive, just click the Save button. Applying the same cross-processing adjustment to other images is a simple matter of loading it with the Load button in the Curves dialog box.