AC's FX Instructions by Adrienne Cleveland
Using the Effects The "Edge" actions don't require you to do anything before running them, with one exception: the ones with "ForegroundColor" in the name require you to select a Foreground Color first. The other actions require you to select one or more areas of the image before you run them, using the Lasso Tool, Elliptical Marquee Tool, or some other method. The selections don't have to be exact -- a rough selection will do. Usually, you'll want to select the main subject(s) of the images. Everything you don't select will be considered to be "background," and will be adjusted separately. The selections are "feathered," or softened, meaning that there is some overlap of the background effect into the selected area. Some Examples
Here's how I selected the Dogwood blossom before running the fade background action on it. Notice that I didn't make any attempt to be exact :) In fact, I stayed well away from the blossom, to lessen the changes to it caused by the feathering. Roll your mouse cursor over the image to see the "after" version.
With the iris, I kept my selection closer to the flower. Roll your mouse cursor over the image to see the effect of running the "Dark Dreams" action.
For this image, I selected the hills and a couple of areas of the field. Roll your mouse cursor over the image to see it after running a Fade Background action. You can see that the sky and part of the field were darkened, while the hills and other selected areas remained mostly unchanged.

For more examples of the effects, see one of the following pages:

this page for Photoshop

this page for Photoshop Elements 1-5

this page for Photoshop Elements 6

this page for Photoshop Elements 7 and later