Try to use the closests to the original photo quality as possible. Some apps will downgrade the photo quality after you edit them on your phone. Be sure to check Save options and make sure they are set to Original quality or whatever is the Maximum quality setting available.

Iphone users: Apple often gives you the option to share or send photos in High quality, but this is not the best quality. Look for Original quality setting and use that option if available.

If the phone quality is too low, you may request in the Photo Services options, to have us Enhance the quality. This has mixed results but generally can double the clearity of a old or fuzzy photo.