There seems to some confusion amongst the retouching masses as to which dodge & burn method(s) work best. Before we get into that debate let's simple ask the question...
What exactly IS dodging and burning? Well if we ask Wikipedia we get something along these lines...
"...A technique used during the printing process to manipulate the exposure of a selected area(s) on a photographic print, deviating from the rest of the image's exposure. In a darkroom print from a film negative, dodging decreases the exposure for areas of the print that the photographer wishes to be lighter, while burning increases the exposure to areas of the print that should be darker.
Any material with varying degrees of opacity may be used, as preferred, to cover and/or obscure the desired area for burning or dodging. One may use a transparency with text, designs, patterns, a stencil, or a completely opaque material shaped according to the desired area of burning/dodging."
With the dawn of the digital age came the use of imaging editing programs(Photoshop) that had dodge and burn tools within the application. To be quite honest, the Dodge and Burn tools in Photoshop work just fine. However, dodging directly onto a pixel defeats the benefit of digital imaging so I prefer to use layers to keep my color, retouching and effects separated for more control of the retouching process. There are a few schools of thought as to which method of dodging and burning is best. Personally, I prefer using Adjustment Layers rather than the "old school" Overlay mode technique. So... before I confuse you any more than I may already have... Let's dig into the topic a bit further.
The Overlay Mode Method
In this first tutorial we discuss the very popular Overlay Mode technique for dodging and burning. Simply put, we place a single 50% gray layer over the pixels we want to affect and use Photoshop's built-in Dodge and Burn tools to do our dirty work. I explain the pros and cons of this technique a bit further in this 5 minute tutorial.
The Curves Method
This technique works the same way as the previous method except for a few small, but very important distinctions. For instance, I don't like the Overlay Method due to the "gray effect" that happens if you lighten a pixel more than 50%. What happens is the color underneath your dodging begins to fade and go gray. With Curves, this is easily controlled as the nature of Curves creates a smoother color transition. This and the fact that after the dodging has been done, the user can then adjust how light the final dodging or burning is by adjusting the appropriate Curve adjustment layer. Don't let me confuse you... watch the video and you'll see exactly what I mean.