Ordering photographic prints is easier when size, crop and finish are decided before files are submitted. A print is a physical object, so consider where and how it will be viewed.
Confirm the crop at the final ratio
A camera file and a chosen paper size may have different proportions. Preview the full image and the proposed crop, paying particular attention to faces, hands and objects near the edges. Decide whether a border is preferable to removing part of the picture.
Check the required file format and any sharpening guidance. For a set of prints, use consistent naming and quantities so that similar-looking files are not confused during ordering or delivery.