Monthly maintenance can help keep computers running fast and free of errors. Here are some steps that I follow for my multiple computers:

MAC
1. Software Update: under the apple menu
2. Verify/repair disc: use disk utility in Applications > Utilities
3. Empty trash
4. MacJanitor: a free download
5. Disc Warrior or Techtool Deluxe
6. Delete browser artifacts & favicons: reset Safari and any other browsers
7. Shock RAM: restart computer holding CMD+Option+R+P
8. Check Activity Monitor for available disc space in Applications > Utilities

PC
1. AdAware: a free download to remove spyware
2. Delete cookies: found under user folders
3. RegCleaner: a free download to clean registry
4. AntiVirus: Norton is a good one that also removes spyware
5. Delete unnecessary temp files: run search for *tmp, ctrl+A, delete
6. Scan for errors: right click on hard drive to access
7. Disc Clean-up: right click on hard drive to access
8. Defragment: right click on hard drive to access
9. Windows Update