InfoPass is a free USCIS service that lets you schedule an appointment with a USCIS Officer at their offices using by using the internet and then printing out your appointment time and date. Such appointments can be rescheduled on line. InfoPass is available in 12 languages but don't assume that any language other than English will be spoken at your appointment. Without this type of appointment you cannot enter a USCIS office and speak with an Officer. USCIS forms can be downloaded from their website and some can be obtained at the interview. Generally, very few USCIS petition types can be filed at such appointments.
You can only enter their offices, up to 15 minutes early and must have proper government issue identification. Cameras, cell telephones with cameras, food, drinks, and dangerous items are not allowed. So leave them in your car. You will be processed through a scanner and your bags will be checked.