How Do I Sell My iPhone Online Without Getting Scammed?

Christopher plans to upgrade to the iPhone 4 and get rid of the deadweight that is his current phone. His requirement is that he not be murdered, attacked or fleeced during this transfer of property, so he’s asking for your tips on how to protect himself during the process.

Christopher writes:

I am faced with a dilemma that I am sure is not unique to myself right now. I was wondering if you could offer myself and the many other readers in this situation any helpful advice.

I am planning to update my ‘iPhone 3g ‘to a ‘iPhone 4′. This leaves me with an extra phone around. I have seen that I can sell the phone for more than I initially bought it for (on contract) via eBay or craigslist. I am a bit hesitant to use either of these services but the sale of my old phone could definitely help pay for my new phone.

I have posted it on eBay and Craigslist so far and have gotten some responses to the CL post. But I am really nervous that I will get scammed. What requests should I make of potential buyers? Do I ask to deal in cash only, in person? Is there a safe way to do
this?

Online selling extraordinaires, what should Christopher watch out for and how should he proceed?