Ok, I admit I don't have a clue how to do this, being that I've never done it myself But I swiped this link with someone asking the same question, maybe it will help you...
When you block a person, they can no longer invite you to a private message or post to your profile wall. Replies and comments they make will be collapsed/hidden by default. Finally, you'll never receive email notifications about content they create or likes they designate for your content.
Note: if you proceed, you will no longer be following .