I want to clear memory of i850 phone?

I have switched carriers and want to sell my old phone. I would like to clear off the contacts, etc. on this before I sell it to someone else. I don't need the sim card, so I would like to sell that too. Can I clear it off so my personal data is not left on it? Should I sell it with the phone or separately?I want to clear memory of i850 phone?
Do a master reset on the phone i think the code is 0000