There are two ways to create an Apple ID in iTunes.
The main way is to actually click "Create Account" in the Store menu, which is what most people tend to do. If you do it this way, you won't see "None" listed in the payment options—you have to choose a method of payment to proceed.
The second way to get to the very same account creation walkthrough is to try installing a completely free app while not signed into an account. There's just one thing that's different if you do it this way; there's an option for "None" at the end of the payment methods.