Make Your Facebook Account Private

Facebook recently (in December, 2009) unveiled a radically revamped set of privacy controls. They are better and more forward-thinking than its previous efforts, but Facebook made one very important change in late 2009: almost all user data is now made public by default.
Facebook users were asked to verify their privacy settings using Facebook's "Privacy transition tool" that recommended some default settings. Oddly, the suggested defaults made most profile settings, photo uploads, status updates and application settings viewable by everyone on the internet. This means the whole world could see everything Facebook users post if they didn't change the defaults.
For more details on these privacy changes, see the Electronic Frontier Foundation's overview.
The most invasive part of the policy for most people will be the public search results settings. This means if they post something and later decide they want to switch to a private profile, those embarrassing posts will remain in search engine indexes.
The good news is that Facebook actually now offers more fine-grained controls over which bits of personal information you share than ever before. The bad news is that the high level of control makes preserving your privacy a fairly complex process. There isn't a simple check box that says "make my profile private."
But fear not, we've got you covered. Follow these instructions below.