For spots and minor skin blemishes use the Spot Healing tool. Use the square bracket keys to adjust the size of the brush so that it is about twice the diameter of the spot you want to hide, and simple click on the spot.
The tool samples the immediately surrounding area and hides the spot by covering it with pixels that match the surrounding skin.
You may run into problems if the spot you are trying to hide is close to a dark area or some other detail. If this happens use the Healing Brush instead.