Applying for U.S. citizenship ("naturalization") isn't always as simple as it seems. Before granting you citizenship, U.S. Citizenship and Immigration Services (USCIS) looks at your current situation and a lot of things that happened in your past. Some of those things can delay or even prevent you from getting citizenship unless you understand how to explain them to USCIS.
If you have any of the issues discussed below, you should definitely hire an immigration lawyer to help you apply for U.S. citizenship. The time to hire the lawyer is before you apply. Don't wait until you've spent the money applying only to find out you're not eligible for citizenship.
If you were arrested or convicted for something minor more than five years ago (or more than years ago if you're applying as the spouse of a U.S. citizen), you might not need a lawyer when applying for citizenship. Just make sure you tell USCIS what happened, even if your record was sealed or expunged.
If you were arrested or convicted more recently than that, however, or if at any time you were convicted of a crime that you're not sure is considered minor or not, you need to speak with an immigration lawyer to find out if you can apply for citizenship now—or ever.
Some crimes for which a person was convicted after November 28, 1990 are considered "aggravated felonies," which will permanently bar you from citizenship. Figuring out what's an "aggravated felony" is best left to an expert.
If you were arrested, charged, or convicted of any type of crime recently, a lawyer may tell you to wait a while before applying for citizenship, or be able to convince USCIS that what happened doesn't affect your "good moral character."
Questions 1 through 44 of the citizenship application Form N-400 (12/23/2016 version) are designed to find out whether you might be ineligible for U.S. citizenship. Take a close look at those questions before you apply.
A "yes" answer to any of them doesn't mean USCIS must deny your application, but depending on your explanation, it could. You are going to need an immigration lawyer's help to know whether you should apply now, apply later, or never apply at all. The lawyer can also help explain to USCIS what happened and why it might not matter.
USCIS has special rules making it easier and quicker to apply for citizenship in certain situations. Most of these situations involve persons who are overseas because they or their spouse is working for the U.S. government, or they're in (or have been in) the U.S. armed forces. If you're planning on taking advantage of special rules to naturalize, or you're not sure if you can, you need to consult with an immigration lawyer to find out what's involved.
You should definitely hire an immigration lawyer to help you with the citizenship process if you're having difficulty following instructions on how to do it yourself, or if you start it yourself and find that you have too many questions about how to fill out the form or what documents you need to send or bring to your interview.
If you don't want to have your application delayed or denied because you made a mistake on the form or didn't give USCIS the right type of evidence it was looking for, just a hire a lawyer to do it for you.
If USCIS denies your citizenship application, it will send you a notice telling you what the problems were. If you don't want to give up trying for citizenship, you definitely need to see an immigration lawyer at this point.
The problems might be something the lawyer could have helped you with when you applied and can now fix, or maybe the lawyer would have predicted that you would get denied and told you not to apply. Let the lawyer tell you whether you can challenge the denial and, if so, you probably want to hire the lawyer to help you from this point forward.