Many of you are experienced Admins.
There are many things that are 'for sure, do this with YaBB'
I'll start with this one.
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Use the built-in YaBB Backup if possible. It supports a variety of backup methods that will work on most servers.
Each works a tiny bit differently. The Tar methods are best suited to linux/Unix servers where you have shell access. The file ownerships and permissions can often be preserved if you have command line access. The ZIP methods, as far as I know, don't offer this.
Issues:
Very large backups can cause timeouts on servers. These may be beyond your ability to fix/or be host-only fixes. If you have a big Attachments folder, you may want to consider Periodic separate backups for it.
Although YaBB Backup does not currently supported automated backups, you can schedule a 'reminder' that will be visible to the Admin when logged in. The reminder is basically just like 'Maintenance Mode'.
If you really don't understand how you would restore incremental backups, stick to the Full Backup methods. This is particularly true if you download the backups. Small forums can live on once-a-week full backups. Larger ones need to consider incremental daily backups + a weekly Full backup.

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OK - who is next ???