Visitor Visa - B2

Myself & my wife had booked USA tour through renowned tour company in Mumbai by paying hefty advance. They arranged for visa appointment. For the said appointment I spent lot of time preparing complete documents file. We thought that as we have tour company letter & all the relevant documents, the consular officer will give visa easily after seeing the file. But it was not so easy. The consular officer did not bother to look at the file. Obviously booking tour through renowned tour company did not matter at all.
 Full interview was totally verbal covering topics like tour itinerary, cost of tour, means of financing, my source of income, investments etc. No papers were asked or seen.
Subsequently my wife was asked questions on her source of income, no. of children, where they stay, what they do? How many grand children & where they stay. I was told not to intervene.
All depends on how fluently & convincingly you reply. Your getting visa totally depends on impression carried by the consular officer about your truthfulness. If you fumble while answering you are in trouble.
So our advise is not to book tour before getting visa & prepare thoroughly for oral interview.