How do I edit friends/people I'm following?

Your friends appear in the sidebar on the left of your profile page.
Click on the little edit icon, which brings you to your Friends List.

There you can do the following:

• Send a smile to your friends.
• Edit whether you know them personally or not.
• Add or change your private note.
• Decide whether or not this friendship is publicly shown.
• You can also delete a person from your friends' list here.

In the tab on the left, you'll find a list of people you follow. Here you have the same functionalities except that you can't mark them as personally known.