The System Preferences You Should Be Using ~ KrobKnea

In my mind, exploring the System Preferences section should be job one of every Mac user. These menus contain a plethora of essential security, privacy, and family friendly settings that should be setup as soon as you pull your Mac out of the box.
In this tutorial I will show you how to use and set the following preference panes:

Users and Groups
Parental Controls
Security and Privacy

Screencast

Users and Groups

Whether it is just for a moment or on a more continuous basis, at some point in time you will be asked to share your Mac with someone else. Having alternate arrangements in place ensures your personal settings and information are protected.
The first scenario I will show you is great for those one-off occasions when someone needs to use your computer for a short amount of time, but there is no need for long term sharing.
From System Preferences click on Users & Groups then unlock the pane by clicking the lock icon in the bottom left. Enter your administrator password to complete the unlock.
NOTE: You may have to repeat these unlock steps for each System Preference pane we cover in this tutorial.

Once the pane is unlocked, click the Guest User item from the sidebar and make sure the box next to Allow guests to login to this computer is checked. I'll go over the parental controls in a later part of this tutorial, but for now just know that it is here and can be enabled or disabled as well.

If a friend or family member needs to borrow the computer for a bit, they can use the Guest User account. Not only is it password free and therefore easy to access, but when they sign out all the information and files from the home folder will be removed. Not to mention that they won't be able to snoop any of the files in your folders.
If you will be sharing your Mac as an ongoing arrangement, then you will want to create an actual user account for each person using it.
To set up a new user, click the + at the bottom of the left sidebar. Select the group you wish to add them to and finish filling out the form with their name, username, and password. Lastly, click Create User.
Now each user will have their own set of login credentials. They will also have their own files, folders, and personal settings. Just remember to log out of the computer when you are done using it by pressing Shift Command Q.

Parental Controls

Once you have more than one user on the computer, the need to control how the computer is used or what it is accessing quickly becomes clear.
Go to System Preferences then Parental Controls. You may need to unlock this pane as you did before. Once unlocked, you will be presented with a list of users that you can assign parental controls too. You can limit access to:

Applications
Internet
People (specifically their email, iMessages, and Game Center interactions)
Time of the day

The list of controls you can enable/disable here are grand. Thankfully, they all come with their own explanation, so I won't be going over each and every one. I would recommend setting limits on applications to those only from the App Store, limits on certain times of the day, and disabling the camera. But these are just a few of the available options, so go exploring and create controls that best fit your needs.

Security and Privacy

Now that you have set up a secure and easy process for your computer to be shared, I want to show you how to keep the rest of the world out. Most of that will be done in the Security and Privacy menu from within System Preferences.
The Security and Privacy preferences are broken down into four tabs. I show you each one.

The General Tab

Here you can reset your password, show a message when the screen is locked, disable automatic login, and select the source for any applications. One lesser known trick hides itself under the advanced section though.
Click Advanced and check out the first option. The ability to have your computer self-logout after a set time of inactivity could be very valuable!

FileVault

If someone snatches your computer and removes the hard drive, you can rest a bit easier by keeping you data encrypted via FileVault. FileVault encrypts your data with XTS-AES 128 encryption. The initial encryption is fast and unobtrusive, so you don't have to worry about slowing down your productivity either! This feature is a must use if you keep ANY personal data on your computer.

Firewall

Most residential and commercial routers do a great job letting the good internet traffic in, while keeping the bad stuff out. But if you spend a lot of time in coffee shops, airports, or other open wireless networks, turning on a firewall at the computer level is a great idea.
Click on Enable Firewall, then Firewall Options. The easiest way to keep yourself safe is to simply check the box next to Block all incoming connections. Your screen should look like this:

Privacy

Lastly there is the Privacy tab. From within this tab you can control which applications have access to personal information like your Location, Contacts, Calendars, Reminders, or full Accessibility. Go through each one and make sure that only the apps you are comfortable giving that level of access to have it.

Conclusion

Computers have managed to work their way into every facet of our lives. Many people don't take the time, unfortunately, to consider just how much sensitive information is stored on these computers. Tax documents, personal photos, banking information and other sensitive data is just a click away.
Spending just a few minutes configuring these settings will equate to a much safer, and ultimately better night's sleep for you and anyone with whom you share your computer.

KrobKnea