There are two types of US visa, immigrant visa and a non immigrant visa. To get visa firstly you must have a valid passport. Then as per rules and regulations, you have to submit all the documents and complete the formalities that US government asks you to fulfill. If you get through hall this then you will be called for the visa interview and if you perform well, you will be given the visa. If you do not perform up to the interviewer’s expectations, you may even get rejected. So always be prepared when you go for the visa interview.