How do I permanently erase my entire MacBook Pro 2011?

Question

I am giving my Mac to somebody and don't want any recoverable traces of me to be on my computer. It's a MacBook Pro 2011 13" but it has Yosemite 10.10.1

Answer 1

Before Selling or Giving Away Your Pre-Lion Mac
Deauthorize your computer from iTunes, if applicable.
Back up your data using Time Machine or other backup methods for OS X Mavericks or Mountain Lion.
If you use Find My Mac or other iCloud features on this Mac, complete these steps:
Back up your iCloud content.
Choose Apple Menu () > System Preferences, then click iCloud.
Deselect the Find My Mac checkbox.
Sign out of iCloud. When you sign out of iCloud, you're asked whether you want to remove iCloud data from your Mac. Removing iCloud data in this way makes sure that the data isn't also removed from any of your other devices that are using the same iCloud account.
If you're using OS X Mountain Lion v10.8 or later, sign out of iMessage:
In the Messages app, choose Preferences > Accounts
Select your iMessage account, then click Sign Out.
  5.  Follow these steps for installing the original version of OS  that came with the computer.
     1. Boot the computer using the Snow Leopard Installer Disc or the Disc 1 that came
         with your computer.  Insert the disc into the optical drive and restart the computer.
         After the chime press and hold down the  "C" key.  Release the key when you see
         a small spinning gear appear below the dark gray Apple logo.
     2. After the installer loads select your language and click on the Continue
         button. When the menu bar appears select Disk Utility from the Utilities menu.
         After Disk Utility loads select the hard drive entry from the left side list (mfgr.'s ID and
         drive size.)  Click on the Partition tab in the DU main window.  Set the number of
         partitions to one (1) from the Partitions drop down menu, click on Options button
         and select GUID, click on OK, then set the format type to MacOS Extended
         (Journaled), then click on the Apply button.
     3. When the formatting has completed quit DU and return to the installer.  Proceed
         with the OS X installation and follow the directions included with the installer.
     4. If you are planning to sell or give your computer away, then do the following:
        After you reformat your hard drive and reinstall OS X, the computer restarts to a
        Welcome screen and asks you to choose a country or region. If you want to leave
        the Mac in an out-of-box state, don't continue with the setup of your system. Instead,
        press Command-Q to shut down the Mac. When the new owner turns on the Mac,
        the Setup Assistant will guide them through the setup process.
Note: Portions of the above have been copied from What to do before selling or giving away your Mac - Apple Support.