Before we talk about some basic tools for locking down Facebook, let's go over the #1 rule of Social Media:
If you don't want the whole world to see it, don't put it online.
Things happen. Facebook has messed up privacy settings before and exposed private information. Accounts get hacked. Companies go out of business and sell data. I could go on and on. If it's going to get you in trouble at work/home/wherever, think twice before putting it online because the internet is forever.
That said, there are a few easy ways to tighten up your Facebook account.
Step 1: Create a Friend List for limited access Facebook Friends
First, click on the Friends link from your home page.
Next, click the "Create New List" button.
Give your list a meaningful name. Mine's called "Minimal Access People".
Step 2: Lock down your profile
Go to the "Privacy Settings" of your account.
Click on "Profile"
Here's what my Profile privacy settings look like. You can see how some items are open to all of my Friends and some are open to all of my Friends except those on the Minimal Access People list.
The above is achieved by editing the "Custom Settings" of each profile item. Here's a drilldown of the Education settings.
Step 3: Lock down photos
The most important Photo privacy setting is the "Photos Tagged of You" setting (which is part of your Profile privacy settings).
This setting is great because it applies to any photo of you, no matter who the photo actually belongs to.
You can also control the privacy of individual Photo albums which is handy but, unfortunately, you have set the privacy of each album individually.
And lastly, you can completely lock certain people entirely out of your photos.
This is done via the "Applications Settings" of your "Privacy Settings". Just click on "Edit Settings" next to the Photos Application
Once you're there, you can set custom settings to control who can access your Facebook photos.
Step 4: Yay!
There you have it, a few basic ways to lock down your Facebook account. Hopefully this gives you a small degree of comfort about who gets to see what about you.
But always to try to keep in the back of your head what would happen if the above doesn't work.