how can i block certain friends from seeing things on my facebook page?

[Cayla]

You can go to privacy settings and click the custom option. Click the link near the bottom of the grid list and it will direct you to the different posts, photos, updates, etc to which you can choose who sees what.

To choose someone specific, click the "customize" option in the drop lists beside each category, then type their name.

You must add the person first to do so, though.