In step 7 you need to run the restore WITH NORECOVERY. That leaves the DB nonoperational and able to restore additional backups (differential or log). If you run the restore with the default options, SQL recovers the database and brings it online and no further backups can be restored.
Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability