The official advice of the US Department of State is:
We cannot guarantee that you will be issued a visa. Do not make final
travel plans or buy tickets until you have a visa.
You should have travel plans, including a full itinerary for your proposed visit, to show that you've through through your plans and know what you'll be doing, but do not book anything non-refundable, so you aren't risking losing the money for the tickets.
US visas are primarily issued on the basis of the application and the interview, and not additional documents:
Why didn’t the Consular Officer look at my documents?
Applying for a
non-immigrant visa is not a documentary process. Consular Officers
never rely only on documents, although they may help support
information you provide at the interview. If the Consular Officer made
a decision in your case without reviewing documents, it was because
the circumstances of your situation were clear. If your visa was
refused, it is highly unlikely that any document you could provide
would significantly alter the Consular Officer’s decision about your
That said, the ustraveldocs site (the scheduling provider used by US consulates in India) lists several supporting documents you should bring to your interview (beyond your appointment letter, DS-160 confirmation page, and current and all old passports):
- Current proof of income, tax payments, property or business ownership, or assets.
- Your travel itinerary and/or other explanation about your planned trip.
- A letter from your employer detailing your position, salary, how long you have been employed, any authorized vacation, and the business
purpose, if any, of your U.S. trip.
- Criminal/court records pertaining to any arrest or conviction anywhere, even if you completed your sentence or were later pardoned.
They also list additional types of documents you might bring depending on your status and the purpose of the trip, such as bank statements or proof of your position in the company.
The consulate employs local staff who are well trained in verifying documents and spotting fakes. They can call banks and employers to confirm that applicants haven't supplied false information, and may report fraud to the local police (in addition to denying a visa, naturally).