To remove someone from your friends list while in the world, right click their avatar and select remove from friends. To do it from your profile. click on the view/edit friends link just under where it displays who your guide is, and check the box/boxes of the people you want to delete. Then click on the delete tab. You can only do this a page at a time.
This is also how you would rank your friends. By checking the box and in the other box under the image you would type 1,2,3 etc and click on set rank. Again, can only be done a page at a time.
Hope this helps.