Here is a good example of how a photo can be greatly enhanced by Photoshop.  The picture on the left is the actual picture I shot using the 3-point lighting system.  As you can see, even with three lights pointing at the figure and white backgrounds, the picture still shows up a little dark.  This is where Photoshop comes in.  Here are the before and afters of the same photo.

To start off, the very first thing you want to do is resize your image.  Most digital cameras will have your pictures in 800x600, 1600x1200, etc.  Which means they are way oversized to fit on most computer screens.  The picture on the top left is resized to 300x400 pixels.  Simply take your original photo and go to IMAGE then IMAGE SIZE to resize your picture.

Next, we're going to start the white backgrounds.  Select your BRUSH TOOL from the menu on your left and select "white" as your foreground color (which is the left color on your palette).

Now start filling around the edges of the figure.  This basically erases and paints over your original background and hides anything you don't want the viewer to see like parts that are accidentally left on the table, your fingers holding the figure or whatever.  Use a bigger brush size to fill the majority of the background.  

When you get close to the figure, simply RIGHT CLICK your mouse to bring up the brush options, choose a smaller brush size (or you can select it at the top menu bar - see below).  You'll probably need to zoom in a little to get the harder cracks and crevices and use a much smaller brush size to get into the body area.

Once the background is completely filled in white and you are happy with the end results of what it will look like, it's time to make the picture a little more "clear."  Photoshop has a great tool called AUTO COLOR to correct contrast, brightness, hue and saturation, etc.  Auto Color basically makes your picture's color the way the colors should look.  Because Photoshop sets a standard on the color scheme, it's not always correct and it's up to you to adjust it to your liking.

Here are the results after the AUTO COLOR feature is carried out.  As you can see, the skin tone on the figure looks slightly more reddish than yellowish in the pictures above.  It's also slightly more brighter than before.

It's still not as bright as I want it to be so we'll go ahead and adjust the brightness and contrast levels on the picture again.  Go to  IMAGE / ADJUSTMENTS / BRIGHTNESS / CONTRAST and adjust the levels until they look right to your eyes.

Photoshop has pre-made image effects they call "filters."  Different filters give you different effects.  The SHARPEN tool is great for image enhancing.  It basically takes the brighter areas and enhances its surrounding to give you a more sharper edge.  Click on FILTER / SHARPEN / SHARPEN.  I like to use the "Sharpen" filter more than the "Sharpen Edges" because it enhances the whole picture and not just the edges of the picture, but you do occasionally need to enhance just the edges too so both these filters are equally important.

Here is the final and end result of the picture you see above.  As you can see, Photoshop is great for image enhancing.  While it may cost quite a bit to purchase alone, it is relatively cheap if bought with a new computer, on eBay, or by file sharing through Kazaa.  Photoshop is a worthwhile investment if you plan to work with figures for a long time or even if you want to enhance regular family photos too.