The eyes are one of the most crucial parts of a person when it comes to portraiture and retouching, as they are the first thing a viewer looks at and generally the establishment point of human interaction. This helpful tutorial will give you a complete guide to retouching eyes to give them a natural, vibrant look that instantly draws the viewer in.
Coming to you from Jesus Ramirez of the Photoshop Training Channel, this video will give you a start-to-finish look at how to retouch eyes in your portrait work, including sharpening, dodging and burning, and even changing their color should you so choose. Of course, the first thing to note is that it's important to start with a properly sharp photo; no amount of Photoshop can fix eyes in a photo that missed focus. The other thing to note is that it's particularly easy to go overboard when it comes to retouching eyes and end up creating an artificial look, so be sure to remember that less is more, and don't be afraid to adjust the layer opacities to taste after you've done your work. I personally spend probably the majority of my retouching time on the eyes; I think they can really push a portrait over the top.
Just don't overdo it!
One of the best tuts I've seen in a long time - a treasure trove of shortcuts as well. great job.
Best insight was to burn the top of the iris under the eyelid -- really helps keep the eye from looking fake. And agree with Mr. Perrin -- just not overdoing it is about the best advice anyone can follow.