If you are missing any of these documents you may be denied entry to the U.S. Depending on what documents you are missing you may also be sent to Secondary Inspection. Learn more about what Secondary Inspection is from the Department of Homeland Security.
It is best to apply for a visa in your home country. If you apply in a third country, expect processing delays. At the consulate/embassy you should provide:
If you are an F-1 or J-1 student / scholar, traveling to a contiguous territory (Canada or Mexico) or the adjacent islands of the Caribbean (see below), you do NOT need to obtain a new visa stamp to reenter the U.S. To qualify for this privilege, you must:
*NOTE: The special exemptions do NOT apply to students who are citizens of the countries named above and traveling to their home countries. In those cases, students must obtain an F-1 or J-1 visa to re-enter the U.S., except for Canadians. Please note that it is more difficult to apply for a U.S. visa while in one of these countries.