The process immigrants have to go through to obtain U.S. citizenship is notorious for being long and complicated, but many citizens who have gone through it are glad they did. The U.S. Citizenship and Immigration Services will handle your citizenship application, so it is in your best interest to become familiar with what they expect.
Before applying for citizenship, there are certain criteria that you should meet. You must be at least 18 years old with a green card and have lived in the United States lawfully as a permanent resident for five years or more. However, there are exceptions for those who are spouses of U.S. citizens and refugees. To be considered as a permanent resident for the purposes of citizenship, you must have been physically present in the U.S. for at least half of the five years. You may not spend more than a year at a time outside of the U.S. or establish a primary home in another country.
In addition to age and residency requirements, there are personal requirements that you must meet for your citizenship application to be successful. You must have what the USCIS considers to be good moral character and you must swear to be loyal to the U.S. and that you believe in the country's principles. Also you must be able to communicate in English and pass a test about U.S. history and government.
Once you meet the above criteria, you can apply for citizenship through the USCIS website. The USCIS is very thorough when it comes to looking into a person's immigration history, so you should be honest on your application and provide all required documentation. Once the application is submitted, you will be scheduled for an interview. This is where a USCIS officer will test you on your English skills and your knowledge of U.S. history and government. People over 50 who fit into an exempted category may be able to skip the English test.
The final step is the swearing-in ceremony where you will take an oath and receive a certificate of naturalization. This is where all your hard work pays off and you officially become a citizen of the United States.
Source: "Requirements for Applying for Citizenship in the United States," accessed on August 12, 2014