Using the Patch Tool
These areas will include Skin blemishes, under eye bags, wrinkles, dark spots, scars etc.
After making your selection, click and drag inside of the selection to a similar area that does not have any blemishes.
The Fade Tool
You could use things like the Eraser Tool or a Layer Mask, but the Fade Tool is the best option. You will be able to see your changes in real time and it will allow you to continue patching on the same layer.