Preparing for a visa interview can be an overwhelming experience. Most importantly, you need to stay calm and tell the truth. The more organized you are with your documents the better. If the interview includes your spouse or other family member, make sure that they prepare with you.
Assemble copies of your application documents and any documentation you have that supports your case. This could include marriage certificates, photos, police reports, medical exam reports, passport photos, or anything else relevant to your situation. Review these documents because questions may come directly from the forms you submit so make sure that you know what information was given on the forms.
Practice answering potential interview questions until you become comfortable with them. This can be done with a friend in a pretend interview type setting or simply out loud to yourself.