While Adobe Photoshop CC is a fine tool for this kind of editing, I often turn to Adobe Photoshop Lightroom 5. If you haven't tried Lightroom before, you may be surprised by how intuitive it is. And because it's part of Adobe Creative Cloud, you don't have to buy to try.
GLOBAL AND LOCAL ADJUSTMENTS
When I'm editing a photo of a person, I usually begin with global adjustments — that is, edits that affect the entire image. Figure 1 (to the right, top image) shows an original image from one of my recent shoots. It's a little dark, and some of the background elements are distracting. By making some global adjustments to the white balance and cropping the entire image, you can solve both of those issues.
Once you make some global adjustments, you can move on to local adjustments, which let you fine-tune the image by affecting specific portions of it. For example, this model has a few blemishes. Use the Spot Removal tool in Lightroom to quickly and convincingly remove them.
You can also add drama to a subject's eyes with a couple of tricks. Remove redness with the Adjustment Brush. And drag the Radial Filter tool across the iris to saturate the eye color and pump up sharpness and clarity.
Figure 2 (to the right, bottom image) shows the impressive results of these quick edits.