Provide rich metadata for each entry. Describe the digital object as elaborately as humanly possible.
Include information on how such entry might be related to the Repository's “theme.”
A contributed photo (or video) might need information on where it was taken. Geolocation apps (like “Geolocation” on Android) can help provide the DD (Decimal Degrees) reading for the spot of the image. Or, if you're providing such information after the photo was already taken and away from the spot, use some geolocation service online.
Watch out for possible copyright violation. Err on the side of caution.
For videos with identifiable individuals, seek to have them sign release forms permitting you to have their images uploaded to the repository.
With notes or correspondences, ensure that they do not involve living, identifiable persons, UNLESS you have their consent to have these materials released publicly.
Materials available online or on social media do not have implicit permission to be made available on the repository. Seek permission where appropriate.
Use tags (for major subject areas and other likely identifiers or categories). They facilitate research and help manage the repository more efficiently.
Where appropriate, spell out acronyms, unless the acronym is recognisable enough or is part of the original title.