1
Inspect and preserve
Open the photo, review it at fit-to-screen and 100% zoom, then save a separate working file. Duplicate the image layer before destructive cleanup. Note whether exposure, color, composition, or a distraction is the most visible problem.
2
Correct the whole image
Crop and straighten first. Add adjustment layers for tonal and color changes, making small moves while checking important details. Use layer masks when a correction helps one area but harms another.
3
Finish and verify
Retouch only remaining distractions, compare the edited photo with the original, and inspect edges at 100% zoom. Save the layered working file separately from an exported copy suited to its destination.