Google Drive and Docs Tips
Turn on Spreadsheet Notifications
Use Tools > Notifications to get notified by email when someone changes the spreadsheet.
Notifications are very useful if you need to know when a change has been made to a Google spreadsheet you own or are collaborating on. Go to the Tools menu and select Notification rules. You can choose to be notified when any change has been made, or just when changes are made to a particular worksheet or range of cells. You can also choose to be notified when collaborators are added or removed, or if the spreadsheet is populated by a form you can choose to be notified each time a form is submitted by a user. If you already have enough email, you can limit notifications to a daily update - very handy!