Prep Macbook to go without reinstall

Hi, I bought a A1226 MacBook Pro a while back to see if it was for me, now I have a new MacBook I want to sell the old one and need to prep it for the new owner, however when I bought the old MacBook it came with no disks. The only things I have done that refer to me on the MacBook is use my iTunes account, and log into some websites.

Can anyone advise what I would need to do/check before passing the MacBook to the new buyer.
In Windows you would delete all cookies and internet history which would delete web used passwords, can I do something similar on the Mac? Do I just de-authorise all devices in iTunes to stop my account being used.

Any help appreciated.

Thanks

Thank you for your help and advice