We now turn to how to complete the forms themselves, filing details, who can file, turnaround times, expedites and classification periods, and the like. U.S. Citizenship and Immigration Services (USCIS) Service Center, tips, addresses, and contact numbers are available in our USCIS Service Center Tips, and Contact Information, together with contact information for the National Call Service Center (NCSC). The forms are for the most part self-explanatory, so this covers only possible trouble spots. In general, complete all blanks with the information requested or with either "N/A" or "none," as appropriate, trying as best you can not to confuse the two. "N/A" should be used where the concept at issue simply has no bearing on your matter, such as an "A number" for a nonimmigrant, while "none" should be used, for instance, in response to a request for a middle initial. Legible print is OK, typed forms are better. A number of commercial computerized forms programs are available. Remember to sign all USCIS forms in blue ink.