I have been lurking around this forum anonymously for a while and I thought I would share how a learned to view certain private stuff on Facebook like the wall and photos of people that have not/will not add you as their friend and do not allow non-friends to view their information like pictures or wall. This is almost obvious, is pretty simple and might have already been posted here so if it has been I'm sorry. This will not work for everyone but it has worked for me personally to view the wall and photos of someone I've been stalking for a long time so I know that it does work sometimes.
Some people's Facebook security settings allow friends of friends to view their wall or pictures. If your target has this setting all you have to do is become a friend of one of their friends! Sometimes this might not be possible especially if they only have a few friends or if their privacy settings don't let you see their friends list. The key is to find a friend of your target that is a Facebook friend whore. The person that has hundreds of friends or more. You know that this person will accept a friend-request from anyone so send that person an invite to be your friend. After that person adds you to their list friend, if your target has any settings to let "friends of friends" view their stuff you are in!
moderator edit: slightly modified for readability and moved to the proper section