How do I control who can add me as a friend in facebook?

How do I control who can add me as a friend? 

 

By default, anyone on Facebook can send you a friend request. If you’d like to modify who can send you friend requests:

1. Click the account menu at the top right of any Facebook page and choose Privacy Settings
2. Next to the How You Connect heading, click Edit Settings
3. Select your preference from the drop-down menu next to Who can send you friend requests?

Please note that people you've subscribed to will be able to send you a friend request.