A US visitor visa interview happens at a US embassy or consulate in the country where you live, before you travel — not at the airport when you arrive. It is a short conversation with a consular officer who decides whether you qualify for a B-1 (business) or B-2 (tourism) visa.
Most refusals are not the result of a trick question. They happen because the applicant could not evidence the few specific things the officer is required to check. Here is what those are, and how to prepare for them.

Everything starts with the Online Nonimmigrant Visa Application, Form DS-160. Two details cause avoidable problems:

Schedule your interview at the embassy or consulate in the country where you live. You can apply elsewhere, but the State Department warns it can be harder to demonstrate your qualifications outside your country of residence.
Appointment waits vary by post, season and visa category, sometimes by months. Check the current wait for your location with the official appointment wait time tool before you book flights or commit to dates.
The visitor visa application fee is $185 at the time of writing, and depending on your nationality you may also owe a visa issuance fee if you are approved. Confirm the current figure on the official fee schedule rather than trusting any third-party number, including this one.

The required list is short:
Beyond that, posts commonly ask for evidence of the purpose of your trip, your intent to depart afterwards, and your ability to pay all costs. If someone else is funding the trip, bring evidence of that instead.

The officer is testing whether your visit is genuinely temporary and whether you will leave at the end of it. Evidence of your employment and family ties is usually what carries this, because it shows both why you are travelling and why you will return.
This is the single most common reason visitor visas are refused, and it is worth preparing for deliberately rather than hoping the conversation goes well.

This is the most persistent myth about visitor visas, and the State Department addresses it directly: applicants must qualify on their own ties to their home country, not on assurances from family or friends in the United States.
A letter of invitation or an Affidavit of Support is not required, and in its own words it "is not one of the factors used in determining whether to issue or deny the visa." Bring one if you want, but do not build your case on it.

Be straightforward about your circumstances, your travel history and your intentions. The consequence of not being is severe and permanent.
Under INA 212(a)(6)(C)(i), willfully misrepresenting a material fact — or committing fraud — to obtain a visa or enter the United States makes you permanently ineligible. A fact is "material" if, had the truth been known, you would not have qualified. Because the bar is permanent, it applies every single time you apply again for the rest of your life.
Waivers exist, but the Department of Homeland Security decides them, they are discretionary, and nothing guarantees one. If there is something difficult in your history — a prior refusal, an overstay, an arrest — disclose it and take advice on how to present it. Concealing it is far more damaging than the underlying fact usually is. See the official guidance on visa denials and ineligibilities and waivers.

An approved visa lets you travel to a US port of entry and request admission. A Customs and Border Protection officer makes the final decision on whether you are admitted and for how long. Keep your passport on you while travelling, do not hand it to anyone other than an official acting in their official capacity, and keep your supporting documents accessible rather than packed in checked luggage.
Read your specific embassy or consulate's instructions — the order of steps and the documents requested genuinely do vary by post. Nothing on this page is legal advice; for anything case-specific, speak to a licensed immigration attorney.
If your longer-term route into the United States is an O-1A or EB-1A petition rather than a visitor visa, the evidence bar is different: you are proving recognition in your field. Promo Panda is a PR firm that builds those press portfolios, working with over 150 immigration attorneys on O-1 and EB-1A cases. If that is your path, see how EB-1A media coverage works.