The interview officer is not there to deny your visa. But, if he/she finds some thing wrong with you then the officer wil not hesitate to deny the Visa.
Please take passport, passport picture, DS-156&DS-157 form, appointment letter, salary stubs, experience letters, degree certificates, marksheets, and photocpies.
The officer will start a converstaion like - What is your job role? It is not going to be technical discussion. Be confident, be clear in your presentation.
These days, at Chennai, I was told that they are not giving visas to non-comuter science grads i.e., civil engineering grad applying for programmer analyst. In these cases take enough experience certifcates, computer diplomas etc.
Best of luck.