Open your image in Photoshop
Select the Clone Stamp Tool from the toolbar
Adjust the brush size, hardness, and opacity in the options bar
Hold Alt on Windows or Option on Mac and click the source area to sample
Release the key and paint over the area you want to clone
Resample from different areas as needed to match texture and tone
Use a soft brush for blending and a harder brush for edges
Lower opacity for subtle corrections
Use aligned sampling if you want the source to move with your brush
Use non-aligned sampling if you want the source to reset each time you sample
Work on a new blank layer when possible
Enable Sample All Layers if cloning from the composite image
Zoom in for precise retouching
Re-sample often to avoid obvious repeating patterns
Save your work regularly