I recently was having trouble with my Apple ID and couldn't purchase anything in the iTunes Store. I tried Apple Care, but they couldn't help and had me fill out a form online. After speaking with them, I found Apple's MY INFO page, that allows you to update the information that is associate with your Apple ID.
Even if you aren't having trouble with your ID, it's a good idea to login and check it out and make sure everything is up to date.
How to do it:
1. Open you browser and go to myinfo.apple.com
2. Enter your location, language, and apple ID credentials.
3. Once you login you can then update several pieces of information. The Email address associated with your Apple ID, your primary address and Shipping address, phone numbers - in case Apple needs to call you regarding a support call, newsletter and email subscriptions, and the different types of ways you allow apple to contact you, such as Email, snail mail, or phone.