Just like any nonimmigrant entering the U.S., people entering under the VWP will be examined. An I-94W will be given to you in the aircraft, other carrier, or at the land border. Immigration officers at the port of entry will examine your application and may check your name against various databases to see if you have overstayed any past visa, have a criminal history or are otherwise inadmissible (have AIDS or TB, no money to support your trip, known criminal/spy/terrorist). If that is the case, you will have to return home immediately. There will be no hearing and there will be no second opinion. You are allowed to attempt to return to the U.S. anytime (unlike visa holders that may have to wait for 5 years before trying again if refused entry), but you must leave the U.S. first.

If people who entered the U.S. on visas are deported by the USCIS, they will be a permitted hearing first in front of an immigration judge. If you entered the U.S. under the VWP, if you stay past your 90-day limit, and if the USCIS decides to deport you, you will not have a hearing before being deported. You must immediately leave.

You cannot extend your stay beyond 90 days and you cannot change your status to another category, nonimmigrant or immigrant. For example, if you want to stay longer to see more tourist places or if you received admission into your dream university or got a lucrative job offer, y ou just can't extend your stay or change status, as those who entered on regular visas may be allowed.

If you already entered the U.S. on other non-immigrant visa, upon expiration of authorized duration, you can't change to stay under Visa Waiver Program to extend your stay. Visa Waiver Program is applicable while entering the U.S.

There may be rare exceptions where you are allowed to stay longer, such as a true medical emergency or you need to apply for political asylum.
Also if you marry a U.S. citizen or are an immediate relative of a U.S. citizen (minor unmarried child or parent), you will be able to apply for a green card while you are in the U.S.

If you are coming to the U.S. to work, study, or to immigrate for any other purposes inconsistent with the allowed purposes of the Visa Waiver Program, you will be refused entry.

You may not enter the U.S. by private (chartered) aircraft or other non-signatory air or sea carriers.

After you have entered the U.S. through the Visa Waiver Program, stayed in the U.S. (or, more precisely, U.S., Canada, Mexico and adjacent islands) for any period up to 90 days, and leave the United States, there is no minimum period requirement to stay abroad before attempting to enter again using the Visa Waiver Program. You can enter as many times as you wish. However, that does not mean you can stay in the U.S. the majority of the time. Immigration officers at the port of entry can deny your admission.

If you were ever (no matter how long ago) arrested, convicted of, or punished for a crime involving moral turpitude, you are not eligible for the Visa Waiver Program. It does not matter whether the conviction was recorded or not. If you have any doubts, simply apply for a visa first.

If you were ever charged with drunk driving offense, you should apply for visa first.

If you have minor traffic offenses on your record, you can travel under the Visa Waiver Program as long as the offense resulted in an arrest and/or conviction for the offense.

If your traffic offense occurred while you were in the U.S., if you have an outstanding fine against you, or you failed to attend your court hearing, there may be a warrant out for your arrest. You may have problems entering the U.S. under the Visa Waiver Program. Before traveling under VWP, you should try to sort out the matter with the concerned court.

If you have been refused a visa under Section 214(b) or 221(g), it does not automatically make you ineligible for the Visa Waiver Program. However, you will be thoroughly questioned at the port of entry. You need to carry strong evidence of your intention to depart the U.S. at the end of your visit. You must show the evidence of strong social and economic ties to your home country.

Transiting the United States using the Visa Waiver Program is permitted. However, there are several restrictions.

Destinations:

• Canada, Mexico, or adjacent islands: Can transit the U.S. both ways (initial and return journey) and can use any mode of transport, as long as the total time spent in the U.S., Canada, Mexico, or adjacent islands doesn't exceed 90 days.
  
  
• Transiting to a final destination other than Canada, Mexico, or adjacent islands: Return journey must be on a participating carrier, but not necessarily within 90 days, as you will need a new application under the Visa Waiver Program.
  
  
• Taking up residence in Bermuda, Canada, or Mexico: If you are transiting the U.S. to take up residence in these countries, you must be a legal permanent resident of these areas.
  
  

If you previously overstayed the 90 days permitted under the VWP, you can't enter again using Visa Waiver Program.