Steps for a Genius Bar reservation or a one to one phone call depend on the issue. Generally speaking you go to http://support.apple.com , select your product, and choose Contact Support from the left menu and fit your request into a category or at least as close as you can. Eventually you reach a screen that will suggest a call or you can select a genius bar appointment if one is relevant to your situation. Of course for genius bar appointment you could just call your local store directly if you sure you need that.