The USCIS website has information on all immigration-related topics, ranging from immigration options and form filing to case status checks and the citizenship test.
Besides the different sections of the site, you can also get automated help from a virtual assistant, called Emma. The assistant provides answers in English and Spanish. Another source of automated help is the phone line: 800-375-5283. You can get answers in English and Spanish and information delivered to your phone or email.
If you feel the need to talk to a representative, you can do so by calling the same, toll-free, number given above. Representatives are available 8:00 to 20:00 Eastern, Mon-Fri. If you are calling from outside the U.S., then the number is 212-620-3418.