The day of your N-400 interview, an officer will call your name from the waiting area, walk you to a small office, and ask you to swear that what you are about to say is true.
Then they go through your application line by line. Most of the questions are direct: have you moved since you filed, are you still married to the same person, have you been arrested for anything not already listed. Answer honestly and briefly. If the answer is yes to something new, explain it; do not volunteer extra information.
The civics test is ten questions chosen from the official list of one hundred. You need six correct to pass. Study the current list from USCIS, because a few of the answers depend on who is in office. We give every client the current list and review it with them before the interview.
The English portion is a short reading sentence and a short writing sentence. Both come from a published vocabulary list. If English is hard for you and you qualify for an age and residency exemption, the interview is conducted in your language and you skip these parts.
Bring the originals of everything you submitted as photocopies: your green card, your passport, your state ID, and any court papers if applicable. The officer will hand them back at the end.
Most interviews end with a decision the same day. If it does not, USCIS mails you a notice within sixty days. If you are approved, the oath ceremony is usually scheduled within a few weeks at a courthouse in Newark or nearby.