When retouching portraits and other photographs the Clone Stamp and Patch tools are very powerful. The Clone Stamp should be used when fixing small blemishes like acne or small scars. The Patch tool should be used for larger areas like wrinkles, creases and bags under the eyes. It samples the texture of an area whereas the Clone Stamp copies or clones the exact pixels.
Step-by-Step How to...
1. Open image in Photoshop
2. Create a new layer and name it "clone".
3. Select the Clone Stamp tool. Hold "option" and click on the area you'd like to clone.
Let go of "option" and paint where desired.
4. Make sure you are painting on the Clone layer. Try to "dab" the paint instead of doing long brush strokes. Use "option" to select various parts of good skin around areas to be retouched. Try to match texture and color of skin when cloning. Remember that "Command-Z" is the keystroke used to "undo" an action. Get used to painting and undoing until the skin is properly retouched.
5. Example of partially retouched skin on forehead.
6. Be sure all cloning has been painted on the Clone layer.
Step-by-Step How To...
1. Make a copy of the Background layer and rename it "Patch".
2. Select the Patch tool from the toolbar. It may be nested under another tool.
3. Using the Patch tool, make a selection around the area you want to patch/repair. It is best to select small areas (the image sample below shows a large selection).
4. Click inside of the selected area and drag it to an area of good skin. The area you drag the patch selection to will copy into the originally selected area.
5. A successfully patched area will have skin texture covering blemishes that match the surrounding area.
6. Lower the opacity of the Patch layer so that it blends naturally with the original image.