I've seen some people have it set up that that only people who know their last name or email can request to be their friend. Is there some sort of code or something that does that?

I don't have myspace yet because my school doesn't allow us to have them, we'll get in huge trouble, but I just want to know ahead of time so I can have that right away....

Silly goose, you could of asked me lol instead of posting here. *laughs* But I'll put the answer for anyone else who needs to know.
You go here (http://settings.myspace.com/index.cfm?fuseaction=user.changeprivacy) and simply click on 'Require email or last name to add me as a friend'.

Have a nice day! :)