Erasing my personal info before returning a Macbook

[MN7119]

So I bought the new 13" Macbook and set it up with my Apple iD, etc... However, after playing with the computer for a while I decided to exchange it for the 15". Now I want to return it but I don't know how to get rid of my data that is in there. It is using my Apple iD as Admin user and loaded all my contacts, favorites, etc... How do I clean that up before returning it?

 

[ROLLTIDE1]

Do a clean install of mavericks

 

[ano0oj]

Take it to the store and ask one of the employees to do a clean wipe of the macbook. they'll do it right in front of you and doesn't take nearly as long as deleting/installing new OS