Choose the destination's aspect ratio first: square avatar, portrait post, or wide banner. Crop from the best available original and keep faces, text, or product details away from edges where masks and overlays may cut them off.
Preview the exported image at the actual size and shape, including a circular avatar mask if relevant. Resize from the cropped original rather than repeatedly saving smaller copies. Keep enough surrounding context that the subject remains recognizable without becoming tiny.
The crop should serve the message, not merely eliminate empty space.
Akousa