Here is a bit of a tutorial on non-destructive dodging and burning in Photoshop

Here is the image I am going to use to demonstrate this:

In order to make the dodge and burn non-destructive, I must make a new layer so that it does not interfere without the original image.

In order to create a new layer, click on the "Layers" menu and select "New" and then select "Layer......"

This will open the new layer dialog:

In the New Layer dialog, change the mode to "Soft Light" and tick the " Fill with Soft-Ligh neutral color (50% Gray)" checkbox and click ok

 In the Layers palette you will now see a new Layer that is Gray

 Next step, select the paintbrush and set the opacity to 10% (change to as required)

To dodge, use white on the foreground brush

To burn part of the image, set the foreground brush to black and start painting what needs to be burnt

As you dodge and burn, you will see the Layer darken where you have burned in and brighten where you have dodge the image

 At any time, if you want to see the image without any of the dodging annd burning, you can turn off the layer, by clicking on the eye beside the layer