Unless a remote sync is needed, a local sync on your network is recommended.
There is a forum post on syncing: Sync Types Explained. This is a good place to start.
There is also one specifically about Bonjour: Bonjour Simplified
Sync is also covered in the Help for each application:
- For DEVONthink, sync is covered in the Help > Documentation > In & Out > Sync, Preferences > Sync, and Troubleshooting > Sync Issues.
- For DEVONthink To Go, sync is covered in the ? > Help > Sync section.
Manuals can be downloaded here: Manuals