How to do a clean install of ML

Hey guys, not sure if this is the right forum to post this in, so I apologize if it's not and move it if needed.

I have a Mid 2010 MBP that I bought off the internet (not any store) and the guy I bought it from said he did a clean install from Lion to Mountain Lion last Monday. Some unexpected things happened, so I'm selling it, but just getting it ready for the buyer to set up like it's brand new for him/her. I didn't purchase the OS from my Apple ID so it's not in my purchases tab or whatever.

I'm still getting used to the Mac OS and everything after being a PC user my whole life and so I want to make sure I do it right and don't mess anything up though I don't have really anything on here. I've really only so far surfed the web, used iMessage, and signed into iTunes with my ID so I don't have a whole lot of stuff on here, but I just don't want anything on here for the new buyer.

I've heard you can do command R or command S while rebooting it, but I'm not sure really if that actually works or not.

If anybody could help me out at all it would be much appreciated!!

The problem you're going to run into is the copy of Mountain Lion you have on the machine is not licensed to you. What you're going to need to do is to purchase a copy of ML from the Mac App store for $19.99 and do a clean install with that. If you try to do a clean install with the copy that's on the machine by using the Recovery partition, the Mac App store is going to ask you for your Apple ID before you can download ML. Either way, you'll need to purchase ML.

If you don't have much of your own data on the machine, there's no need to do a clean install of ML. Just follow the directions given here which will guide you on what to do when selling your Mac.