To regulate who can follow you, just do number of things:
1)Tap menu in the lower right corner of Facebook.
2)Click to the bottom of the page and tap Settings and privacy, then Settings.
3)Tap Followers and public content at the bottom of the page.
4)Below Who Can Follow Me, select Friends or Public.
Moreover,You are instantly followed by your Facebook friends. But You can also allow individuals who aren't your friends to view your activity.