Main documents are H1B approval form ( I forgot the name) that states the duration of your work permit, pay stubs from last 2 to three months, a letter from your employer stating that you are visiting you country for Xdays and you will be back to resume work. These are the main documents. but you can take other documents such as, if you had filed tax previously, you can take those documents, your college I-20, transcript, diploma. And once you have your visa, do not forget to get a "shram sukruti" work permit from "shram karyalaya" department of labor located in Teku. Good luck. Don't worry too much. It is very easy to get visa for h1b. I just got asked one question and that was to describe my jub duties.