You can cut out this page and hang it in a conspicuous place to remind you which tasks you should do when. You might also consider adding daily, weekly, monthly, and yearly reminders to your favorite calendar application.
Back up changed files.
Download (but dont install) software updates.
Clean up your Desktop.
Check for third-party software updates.
Back up everything.
Reboot if performance seems slow.
Rotate backups offsite.
Consider clearing certain caches.
Use Software Update to install Apple software updates.