Although most people wanting to come to the United States as a tourist will first have to go to a U.S. consulate and apply for a visa, you may be able to avoid this if you are:
If all these things are true of you, you may enter the United States without a visa, under the Visa Waiver Program (VWP). You’ll want to weigh the advantages and disadvantages first, however. In some cases, people from Visa Waiver countries find it’s better for them to apply for a tourist (B-2) visa.
It's also important to realize that the VWP is not a free entry pass. If, upon coming to the U.S., the border officials determine that your true intent is some activity other than tourism, you may be told that you should have applied for a visa allowing that activity, and sent home.
Although you don’t need to get a visa, coming to the U.S. under the VWP does require some preparation ahead of time. This includes:
Also, before you arrive from a Visa Waiver country, the airline or other carrier will give you a form to fill out (I-94W). This is mostly used to determine whether you are inadmissible to the United States.
After you arrive, the Customs and Border Patrol (CBP) officer will review your I-94W Form and other documents. The officer will check your name against an electronic database to see whether you’ve overstayed any past visas or have a criminal history.
The CBP officers have the power to deny any person entry and insist that he or she return home immediately, with no hearing and no second opinion. People who enter on tourist visas run this same risk, but at least they’ve given their application for entry a “test run” past a U.S. consular official, who would probably deny their visa on the spot and save them a plane trip.
As a Visa Waiver entrant, you would, after being denied entry, be allowed to try to return to the United States anytime. Some people who enter on visas have to wait five years if they’re refused entry. However, you would still have to leave the United States first.