Security checks and the requirement to have an appointment for an interview are the primary causes for delays. The Department of State's (DOS) web information on non-immigrant visas is a good source of current information:

• Visa Information for Temporary Visitors provides general information for temporary visitors to the U.S., including students.
• Visa Wait Times provides approximate wait times for visa appointments and visa processing at each U.S. consulate. Note that appointments for "F" students and "J" Exchange Visitors have priority over other classifications.
• United States Embassies and Consulates Worldwide provides information on procedures, fees, and online application forms.

Another useful source is the the US Immigration and Customs Enforcement (ICE) of the Department of Homeland Security (DHS). Although directed to those arriving in J-1 Exchange Visitor status, their fact sheet Arriving at a U.S. Port Of Entry...What an Exchange Visitor Can Expect highlights the necessary steps and procedures you will encounter when passing through immigration inspection upon arrival at the U.S. port of entry.

Visa Interview Requirement:
All nonimmigrants require a visa appointment. Note that appointments for "F" students and "J" Exchange Visitors have priority over other classifications.

Technology Alert List and Sensitive Areas of Study
Students, faculty and researchers who are considered to be studying, researching or teaching "sensitive areas" as determined by the U.S. government may also be required to undergo security clearances before a visa can be issued. There is a document called the "Technology Alert List" that visa officers consult for this purpose. There are 15 broad subject areas on the Technology Alert List, with detailed specializations within each area. China, India, Israel, Pakistan and Russia have received special mention by the U.S. State Department because these countries are considered to possess nuclear capability that is of concern to U.S. national security. However, even if you are not a citizen of one of the countries listed above, your field of study (especially if it is in the sciences, technology or engineering) might require your visa application to undergo a security clearance REGARDLESS of the country you are from. Such clearances can add weeks to the amount of time needed for visa approval.

Name Check by DOS and DHS
The "name check lookup" is conducted by the State Department at the time of visa application and by the Department of Homeland Security at the port of entry—irrespective of whether the visitor holds a valid visa. This name check has recently resulted in unexpected and severe problems for non-immigrants—some arising from previous overstay(s), others from discovery of a record of illegal activity in the United States, and others because of mistaken name matches with listings in the database.

Special Registration Procedures for Certain Foreign Nationals
Since September 11, 2002, certain non-immigrants were required to be fingerprinted and photographed at district immigration offices and U.S. ports of entry. Special Registrants are also subject to departure procedures from ports of entry specifically designated for departure control. These ports of entry with accompanying phone numbers are listed in the "walkaway material".

Currently, citizens above the age of fourteen of Iran, Iraq, Libya, Syria and Sudan are subject to mandatory special registration at ports of entry. This list is subject to change at any time, and registration may be required of any non-immigrants of any nationality who are deemed by a consular officer or inspections officer to require closer monitoring.