If you're planning a short trip to the United States, you must, with certain exceptions, obtain a "nonimmigrant" (temporary) visa. (For exceptions to this rule, see Nolo's article U.S Immigration Basics -- in particular, the discussion of the visa waiver program.) Below we summarize who qualifies for the various types of nonimmigrant visas. For details, including how to apply for a visa, see U.S. Immigration Made Easy, by Ilona Bray (Nolo).
Types of Nonimmigrant Visas
You must choose the specific purpose of your trip (such as tourism or going to school) and apply for a specialized visa that authorizes that activity and no other. Each type of nonimmigrant visa is identified by a letter-number combination. You may already be familiar with the more popular ones: B-2 (visitor for tourism), E-2 (investor), F-1 (academic or language student), and H-1B (specialty worker). See the chart below for a complete list of the most commonly used codes and descriptions.
Your next step is determining how and where to apply for your visa; for more information, see Nolo's article Applying for a Nonimmigrant (Temporary) Visa or get the book U.S. Immigration Made Easy, by Ilona Bray (Nolo).
Limits on Activities in the U.S.
Your visa allows you to enter the United States and to engage in certain activities while you're there. For example, if you receive a student visa, you're allowed to study in the United States -- but not to work off campus (unless you seek special permission) and not to stay permanently.
How Long Your Visa Will Last
Just as nonimmigrant visas vary in purpose, they also vary as to how long they last. Each nonimmigrant visa is given an expiration date according to what the law allows. Most can also be extended a certain number of times.
An important caution: The expiration date on your visa does not indicate how long you can stay in the U.S. once you arrive. It indicates only the period of time during which you have the right to enter the United States using that visa. How long you can stay is shown by the date on your "I-94 card," which is a small white or green card you'll be given when you enter the country.
If your visa is "multiple entry," however, you can use it to enter the United States again, as soon as you like. If it's not multiple entry, you can use it only once. For information about questions you may be asked when you arrive in the U.S., see Nolo's article Entering the U.S.: What to Expect at the Airport or Border.
For a comprehensive resource that covers nearly every way to legally enter and live in the United States, get U.S. Immigration Made Easy, by Ilona Bray (Nolo).