What are the common mistakes and challenges when using the clone stamp tool?

One often overlooked so under utilised aspect of the clone tool is, I think, the mode option. Especially when correcting skin blemishes, or removing unwanted highlights or shine, changing the mode to lighten or darken (depending on the skin tone and use case) and the clone tool will only apply to the pixels that are darker/lighter than the source selected. Can make for a much more natural effect, as less of an obvious brush.

Common mistakes and challenges when using the clone stamp tool include not changing source points frequently, ignoring lighting and shadows, overusing the tool, incorrect brush size and hardness, cloning from the wrong area, not using layers, forgetting to blend, cloning with unrelated patterns, not zooming in, and ignoring the context of the image.

From my experience this is probably one of the easiest ways to seamlessly correct blemishes and remove unwanted objects to make your work look cleaner and more professional.

This is one of the easiest mistakes to make when using the clone stamp to clean up a background or remove an unwanted object. Vary where you source from, change up your opacity and watch out for those funny little pixels!

The brush you use makes a difference. I prefer soft edges so it’s a soft transition to where I cloned. Typically I need a soft transition. But if the area im cloning is clear and cut then I’ll use a harder brush.

The softness of your brush edge makes a huge impact! Pun intended... Depending on the size of the area you're cloning, you can work your way from the center out and adjust the opacity as you go. But first, always create a new layer!

For me it's making sure I don't remove texture. The quickest way to tell bad photoshoping is the pattern or textural blur from any of the clean up tools (except the patch tool) which is great at capturing and re-establishing texture to an image. But... make sure the texture you are adding back in (should you have removed too much) is at the same focal length as the destination. Marta is a texture Nazi so I always focus on that.

Long time ago when the cloning tools was the only available resource to correct dust particles that the film/negative had after scanning, which took a much effort, specially with medium b&w 6x6 images, as the scanner software that uses the infrared layer to detect and correct these issues, does not work well with B&W, so I spent many hours of cleaning by cloning data adjacent to the dust particle/fiber. The newer versions of Photoshop came with the healing tool, that takes care of cloning while maintaining color/luminosity; also, using a Wacom tablet, makes your life much easier. Today I only use cloning tool on particular situations, when the healing tool does not work properly.