6. How to Auto-Decline Appointments
If you'll be away on vacation or know you have a prior commitment, a handy tool in Google Calendar labs is "Automatically declining events." To turn on this feature, click the gear icon at the top right of your screen and select "Labs." Click "Enable" next to it, then "Save" at the bottom of the page.
This feature lets you block times in your calendar when you know you'll be unavailable. When someone sends you an invite for an event during this time period, Google Calendar will automatically decline it.