Creating a Full Head of Hair/Filling in Bald Spots
Open the photo of someone with thinning hair. The photo I used is shown below. I got this photo from http://www.reflexstock.com/:
Create a new layer by clicking the New Layer icon on the layers palette:
Select the Clone Stamp tool from the Toolbox and be sure that the Sample All Layers checkbox is turned on in the Options Bar at the top of the document window. Select a soft brush and make sure the brush size is sampled to the area you are going to copy.
Click once on the new blank layer you just created to select it then press and hold down the Alt key while you click to sample an area of existing hair:
Start painting with the Clone Stamp tool over the areas of thinning hair. I resampled often in different areas in order for the hair to look natural. Here is my finished product: