Adding more color to an image: sometimes, an image will need just a bit more color. Here, the idea is to add some saturation (not too much, +15 to +18 seems to work well). Notice my wife's skin tone and hair color are more prevelant in the "after" photograph.

Adding contrast to an image: make the dark areas dark and the light areas brighter. The trick is to turn down the brightness and up the contrast. This technique---along with adjusting the saturation---works well with removing the "haze" common to many outdoor photographs. You can see it in action here.

Using the Unsharp Mask: When resizing a .jpg image, the image tends to become somewhat blurry or fuzzy. Utilizing the Unsharp Mask with these settings in Photoshop sharpens the image.