Take a look here:
Read the steps carefully as the order in which you follow them is critical. Note that you can do this only when creating a new Apple ID. You cannot use an existing ID.
You will of course not be able to get anything other than the free apps, iTunes U content or podcasts without entering in some sort of payment method (credit card, prepaid iTunes card, gift certificate, etc.)
Forum Tip: Since you're new here, you've probably not discovered the Search feature available on every Communities page, but next time, it might save you time (and everyone else from having to answer the same question multiple times) if you search a couple of ways for a topic, both in the relevant forums and in the Apple Knowledge Base, before you post a question.
scroll down in this thread until you see a post by texas man. he explains how you can select NONE. its hard to see but its there on the CC information screen.https://discussions.apple.com/message/21286346#21286346