1. Find out if you are eligible
- To apply you must be ONE of the following:
(1) A Lawful Permanent Resident for at least five years and at least 18 years old;
(2) A Lawful Permanent Resident for at least three years and at least 18 years old,
You have been married to and living with the same U.S. citizen for the last three years,
AND Your spouse has been a U.S. citizen for the last three years;
(3) A member of one of several other groups eligible to apply for naturalization (for example, persons who are nationals but not citizens of the United States) and at least 18 years old.
(4) A person who has served honorably in the U.S.Armed Forces, AND If you are at least 18 years old, a Lawful Permanent Resident with at least one year of U.S. Armed Forces service, and you are filing your application for naturalization while still in the service or within six months after the termination of such service. OR You served honorably as a member of the Selected Reserve of the Ready Reserve or inactive-duty status during a designated period of hostilities. You then may apply for naturalization without having been physically present in the United States for any specified period.
More about eligibility can be found at: http://www.uscis.gov/files/form/n-400ins.pdf
2. You will need to fill out and submit form N-400 to your local USCIS office. This form can be found at http://citizenshipeasy.com/citizenship_forms (you can download and fill out this form for free). OR you can use Citizenship Easy interactive, interview style system to fill out this form.
3. After you submit N-400 to your local USCIS office, you will receive a letter from USCIS inviting you to fingerprints appointment.
4. After that you will wait for another USCIS letter that will notify you about you naturalization application (N-400) interview and US civic (citizenship) test. The examples of the citizenship test can be found at http://citizenshipeasy.com/citizenship_test
5. After the completion of the above appointment another letter from USCIS will arrive. In that letter will be a date of naturalization ceremony where you will receive your Certificate of Naturalization.