You can avoid double-booking meetings with Outlook Scheduling Assistant, which allows you to view your colleagues’ availability. Knowing the time availability is not the only benefit of Outlook — Room Finder is another benefit that aids users in finding location availability to meet.

1. From the Inbox, select New Items > Meeting or in the Calendar, select New Meeting. You also can use the keyboard shortcut Ctrl+Shift+Q to create a new meeting request.
2. Add attendees in the To box.
3. Select Scheduling Assistant from the ribbon. You'll see a row for every recipient you entered in the To box. If you want to add more attendees, you can type their name in any blank row in the Scheduling Assistant.
4. Times that your attendees are busy are shown in dark blue. Times that your attendees have a tentative appointment are shown in a light blue hashed block, and times outside of your attendees' working hours are shown in light gray. Select an available time for all your attendees.

Room Finder is located on the right side of the Meeting screen.

1. Click on Room Finder and select the floor you’d like to host your meeting on.
2. Select a location from the list of Suggested conference rooms.
3. The room will be added in the field Required in the meeting screen
4. Title your meeting, add attendees and send.

View more detailed instructions from Microsoft:

• Scheduling Assistant for PC
• Scheduling Assistant for Mac