Prior to Disembarking
You should be aware that a visa does not guarantee entry to the United States. The Immigration and Naturalization Service (INS) has authority to deny admission at the port-of-entry. You should be very careful to have all your documents in order upon arrival. Prior to disembarking from the airplane, the flight attendant will pass out a white-colored form called the I-94-Arrival/Departure Record. You will need to fill out all pertinent information regarding your arrival in the United States.
At the Port-of-Entry
At the port-of-entry, an INS inspector will check the I-94 and your travel documents and stamp your passport and Form I-20 or Form IAP-66 to indicate the entry date, location and non-immigrant classification and length of authorized stay. They will return to you the "Student Copy" of the Form I-20 or the pink-colored copy of the Form IAP-66. The I-94 Departure Record will be attached to your passport.