1. Not Prepared for the Interview
Preparing for interview can better equip and give you confidence in the interview. Researching and preparing well with for commonly asked questions and their correct answers will help a great deal in the interview.
2. Incomplete and Untruthful Information
This is very important as any incomplete/false information can lead to delay. False information can predict your future ability to apply for US visa. It may also cause legal actions against you.