Photos
I would take 2 passport size photos. See travel.state.gov for details. I would also fill out the downloadable form on this site and print it out. That is all you will need for your passport in most cases. As soon as you are done with you oath, go to the nearest service center ( the travel.state.gov site tells you) withe the fee ($55 in personal check and $30 in cash) and apply right away. If your app is filled out and you have your naturalization certificate, pictures and fees then you are good to apply.