You want agent alerts on all severity 20+ errors (you can set them on severity level) and on error 825. If you're doing checkDB once a week, make sure you retain all backups (full, diff and log) for at least a week.
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