Ignore the Dodge and Burn tools
Photoshop's Dodge and Burn tools burn into the pixels and shift colour as they go. Nobody who does this seriously uses them. The non-destructive method is better in every respect and takes one minute to set up.
The 50% grey layer method
- New layer, mode Soft Light, tick Fill with Soft-Light-neutral colour (50% grey).
- Paint with a soft white brush to lighten, black to darken.
- Flow at 2–5%. This is not a typo — the effect should be barely visible per stroke and built up over many passes.
- Alt-click the layer to see the grey map itself, which shows exactly what you have done.
Prefer a gentler result? Use Overlay for stronger contrast or two separate Curves layers — one raised, one lowered, both masked to black — for the most control of all.
What to dodge and burn in a portrait
Work with the existing light rather than against it. Deepen shadows that already fall under the cheekbone and jaw; lift highlights already present on the brow, nose bridge and the top of the cheek. The aim is to reinforce the modelling the light is doing, not to invent a new light source.
Small targeted work pays off too: brighten the iris slightly, deepen the lash line, even out a distractingly bright patch of forehead. Keep it subtle — the effect should be invisible as technique.
In landscapes
Dodging and burning is how you guide the eye through a scene. Darken the frame edges slightly and lift the area you want read first. This is a vignette done with judgment instead of a slider, and it looks far better because it follows the content of the picture.
Check your work
Add a temporary black-and-white adjustment layer at the top of the stack while you work. Stripping the colour out makes uneven tonal work obvious in a way that colour hides. Turn it off when you are done, then check the whole edit at fit-to-screen.