A couple ideas come to mind:
A layer that
softens the skin. You can probably select just the skin (not the eyes or mouth), feather the selection, copy it into its own separate layer, and then apply a small amount of Gaussian blur. It can give a nice softening effect to the skin and might take away some wrinkles. If you do too much Gaussian blur, then it can look plastic-y & fake. You can adjust the layer opacity as needed.
A layer that
sharpens the eyes. Select only the eyes, feather the selection, copy the eyes into its own separate layer, and then apply a judicious amount of sharpening. People are typically drawn to a subject's eyes.
If you're working on eyes, you can also create a layer to
darken the pupils. Make them really black.
If your subject doesn't already have "
catch lights" in her eyes, you can add those in artificially, too.
If your subject needs or wants
alluring eyelashes, you can download some Photoshop eyelashes from the Internet, upload them into Photoshop as a "brush", and then apply the new eyelashes onto your subject. Do an "Edit > Free Transform" on those eyelashes so that they fit exactly onto your subject's eyes.
Does your subject need
redder, more alluring lips? You can select the subject's lips, feather the selection, and copy the lips onto a separate layer. Then do something to the color of the lips...perhaps increase the red saturation as an adjustment layer?
Just a few ideas. Actually, this reminds me of a "disturbing" YouTube video that might help you with your midterm Photoshop project:
http://www.youtube.com/watch?v=iYhCn0jf46U&feature=related
Hope that helps!
