Fill out the USCIS Form N-400 by providing basic biographical information as well as the answers to the questions on the form, as Nolo explains. USCIS uses the form to determine if you meet citizenship eligibility requirements.
USCIS Form N-400 starts out by asking you to indicate the basis of your eligibility, according to Nolo. From there, the form requests personal information, such as you name, whether you've used other names, your Social Security number, date of birth and the date you became a permanent resident.
The form then asks for the best way to contact you as well as information about your residence, parents and criminal record. Since the USCIS usually performs a criminal background check, indicate any information that such a check generates. Also, provide information regarding your education, employment record, marital history and time spent outside the United States, according to Nolo.
The rest of the form goes on to ask for detailed information regarding your citizenship eligibility. If there are questions that don't apply to your situation, you should simply write "N/A" instead of leaving the answer blank. If there are questions that you don't understand, it's best to consult with an attorney, as Nolo advises.