What to add to Wikidata:
- adding labels to items in a language
- adding statements for existing items
- adding items and statements based on a Wiki project
- adding missing items to create links among items
Realistically, it is always a bit of all of that. The people attending are not all the same either, they differ in interest and they differ in skills. One goal for a "datathon" may be the transfer of skills. When this is the case, start with the basics of Wikidata. How to add labels, how to add statements. how to add items.
Another goal is to add information for a specific domain. This may be based on information known to a Wiki project but that is optional. When information for a specific domain is to be worked on, Working together and use as many tools as available makes a real difference.
As a blogpost should not be too long, more later..