Knowing where to start retouching a photo can be a painful thing. Here are some tips to help get you started.

WORK FLOW

Work at 100% magnification

Click your magnifying glass and then in your menu select actual pixels. That's the quick way to get to 100%. When you work at 100%, generally anything you can see here will show in the final print, so it is definitely best to so most of your work here, zooming out only to get an overall feel for the image.

Use the Space Bar to walk over the image

If you would like to make quick work of an image, use your thumb to activate the hand where you can quickly click and drag to walk yourself over an image. Scroll bars are a pain in the butt, don't use them.

TOOLS

Highlights & Shadows

This is probably the most underrated tool in Photoshop, and if CS only had this tool as an upgrade from Photoshop 7, it would be a strong enough reason to upgrade in my opinion. Especially for black and white work, which is how I treated the underexposed bottom of this image. Most of this image was saved by layer composites using this tool.

-Duplicate layer

-Run H&S

-Erase top half

Keep doing this till you're satisfied with the results. There's no magic one click approach, you have to keep an eye on the results as you go and make adjustments.

Dodge & Burn

Dodge and burn the photo like someone in the darkroom would, to adjust exposure. Remember, this is Photoshop. If you're not dodging and burning photos, you're not using the powerful tools that photographers have been using to adjust image exposure for decades. (Think Ansel Adams)

Clone

Detail is often lost in the darks of an underexposed image, as was the case of the gentleman's black vest. There was no detail left in that vest to recover this part of the image. Given that the texture is consistent, and still exists in the lighter part of the vest, this can be cloned back in rather quickly. Depending on the size of the final print, you may wish to give additional time to cloning.

Neat Image

I actually have a nicer version of this image where the skin tones are all smoothed out using neat image, which is an awesome noise reduction program. I added grain back to this image so that it looks more like the original, but not as blotchy as the original.

Smart Sharpen

Learn it, use it, love it. Gives the final output some pop.

Hope that helps some. Like I said, my results were not 100% perfect, but generally I am satisfied with the results given the short time put in. Also, the end result can always make an excellent Black & White.