A full application screenshot often becomes a blur when reduced to thumbnail size. Focus on the result or interface detail that explains the video's task.
Isolate the relevant area
For a chart tutorial, the finished chart may matter more than menus and toolbars. For a settings lesson, one clearly framed control may be the useful clue. Remove unrelated windows and personal information before capturing the source.
Preserve truthful context
Do not redesign an interface so heavily that it suggests controls or results that do not exist. A magnified detail can help, but keep it visually connected to the actual task. Use the correct software version where the distinction matters.
Review alongside the title
Let the title name the procedure while the image shows its outcome or key obstacle. If several labels are required to explain the screenshot, choose a simpler visual. Keep the original capture and edited thumbnail separately so another reviewer can verify what was changed.