Nonimmigrant Visa Requirements
Depending on a number of factors, acquiring a nonimmigrant visa may be easy or difficult. Nationals of some countries may enter the U.S. as tourists without having to apply for a visa under the Visa Waiver program. Most will need to apply with the consulate, however. Applicants should be ready to demonstrate their ties to their home country, showing that they are likely to return home upon expiration of their visa. They should also demonstrate the economic ability to support themselves during their visit to the United States. Finally, they should be ready to demonstrate the qualifications for the visa they are seeking, if it requires special skills, education, or licensing.
Extending or Changing Visas
Certain kinds of visa forbid change or extension. Visa waiver entrants, for example, are not allowed to extend or change their status without leaving the country. Other non-immigrants may have the option to change to a new visa or extend their current one without leaving. In almost every case the application must be filed before the expiration of the applicant's current authorized stay as reflected on the I-94 document they were issued upon entry.
If your I-94 expires while awaiting a decision on a request to extend or change visas, there is normally no cause for concern. Those awaiting a decision are permitted to remain in the country to await the decision. If your application is approved, it will cover the gap; and if it is not, the denial will indicate that you must depart the country within 30 days of receipt of the denial or risk. If you fail to depart within this period, though, you will begin to accrue time unlawfully present and expose yourself to deportation or removal proceedings.
Application for Immigrant Visas
Non-immigrant visa holders should exercise caution when applying for an immigrant visas. Since many non-immigrant visas require that the applicant establish that they don't have the intent to immigrate permanently. As such, it is vital that the individual be aware of the timing of their application as well as how long will be required before a green card will become available in their category, since this can greatly complicate the maintenance or acquisition of a non-immigrant visa. Furthermore, some non-immigrant visas forbid a change of status to an immigrant without departing the country or fulfilling other conditions. Consult an immigration attorney to be sure you don't run afoul of the regulations.