You have to make an appointment before hand. Usually they will not let you go there the very day, at least several days to wait unless it is an emergency.

On the appiontment time, you can go directly, write down your name and ssn on the register book; you also need to fill out some disease history info if this is your first time been there. Then all you have to do is to wair--a nurse will call you and give you regular check ups like weight, blood pressure etc. Then the doctor comes and see you.

About insurance, I think you can call the doctor ('s assistant) and ask if you will be covered before making the appointment.