How do I reinstall Lion to sell my Mac?

Question

I have an iMac Mid-2011 model that I bought from the Apple store. The machine came without installation disks, so I assume it had Lion installed when I bought it. I have since purchased and installed Mountain Lion.
I am now selling the iMac, so I have booted to the recovery partition and run Disk Utility to erase the main hard disk.
Now I want to reinstate Lion so that the buyer will receive the computer as if it had come new from the Apple Store.
I tried to reinstall Lion using the Mac OS Utility and it announced that it would install Mountain Lion, not Lion. It then asked me for my Apple ID and password.
What I would like to know is:
1. Can I just put the machine back to its origianl Lion configuration, as if it had just come from the Apple store
2. If I enter my Apple ID and password, when the buyer gets the machine will he be able to continue to use Lion and will my Apple ID and password be at risk?

Answer 1

Follow these instructions step by step to prepare a Mac for sale:
Step One - Back up your data:
If you have any Virtual PCs shut them down. They cannot be in their "fast saved" state. They must be shut down from inside Windows.
Clone to an external drive using using Carbon Copy Cloner.
Open Carbon Copy Cloner.
Select the Source volume from the Select a source drop down menu on the left side.
Select the Destination volume from the Select a destination drop down menu on the right side.
Click on the Clone button. If you are prompted about creating a clone of the Recovery HD be sure to opt for that.
Destination means a freshly erased external backup drive. Source means the internal startup drive.
Step Two - Prepare the machine for the new buyer:
De-authorize the computer in iTunes! De-authorize both iTunes and Audible accounts.
Remove any Open Firmware passwords or Firmware passwords.
Turn the brightness full up and volume nearly so.
Step Three - Install a fresh OS:
  A. Snow Leopard and earlier versions of OS X
Insert the original OS X install CD/DVD that came with your computer.
Restart the computer while holding down the C key to boot from the CD/DVD.
Select Disk Utility from the Utilities menu; repartition and reformat the internal hard drive (optionally zero all data).
Install OS X.
Upon completion DO NOT restart the computer.
Shutdown the computer.
          B. Lion and Mountain Lion (if pre-installed on the computer at purchase)*
Restart the computer while holding down the COMMAND and R keys until the menu screen appears.
Select Disk Utility from the main menu and click on the Continue button.
After DU loads select your startup volume (usually Macintosh HD) from the left side list. Click on the Erase tab in the DU main window.
Set the format type to Mac OS Extended (Journaled.) Click on the Erase button and wait until the process has completed.
Quit DU and return to the main menu.
Select Reinstall Lion/Mountain Lion and click on the Install button.
Upon completion shutdown the computer
Note: You will need an active Internet connection. I suggest using Ethernet if possible because it is three times faster than wireless.
*If your computer came with Lion or Mountain Lion pre-installed then you are entitled to transfer your license once. If you purchased Lion or Mountain Lion from the App Store then you cannot transfer your license to another party. In the case of the latter you should install the original version of OS X that came with your computer. You need to repartition the hard drive as well as reformat it; this will assure that the Recovery HD partition is removed. See Step Three above. You may verify these requirements by reviewing your OS X Software License.