Backup a mirrored database

I have a client who is worried about his backup strategy. He has two servers
and has succesfully setup mirroring. He wants to be able to automatically
backup databaseA before and after the mirror server becomes a principal.
What is the proper procedure to ensure that a backup job doesn't fail when
the roles of principal and mirror are reversed?
For example. On the principal, my client is doing a full backup on sun,
diff monday to sat and tlog backup every hour. On the mirror he has not
scheduled a backup. If the database fails on tuesday, the backup that would
normally run on the principal server will fail. The mirror server (which is
now the principal) currently doesn't have a backup scheduled. What is the
best practice?
Thanks for any help.
Dan
Thanks for you help.
"Tibor Karaszi" wrote:

> Create the same job on both servers, both jobs are always enabled, and in the job you use the
> sys.database_mirroring catalog view it see if the database is principal or mirror.
> --
> Tibor Karaszi, SQL Server MVP
> http://www.karaszi.com/sqlserver/default.asp
> http://www.solidqualitylearning.com/
>
> "Dan Wood" <DanWood@.discussions.microsoft.com> wrote in message
> news:F9A439EF-A131-450E-A032-12382AE9C782@.microsoft.com...
>