The idea of a personal interview in order to help determine admissibility to Canada can create a lot of anxiety. In many cases however, personal interviews will not be required. An interview will only be required if the Visa officer determines that it is necessary to conduct an interview in order to properly assess whether the applicant qualifies for Canadian permanent residence.
The officer will normally request documentation to confirm employment history, education, parentage of children, marital status or date of birth, although the Visa office can make any reasonable request for documentation. If the applicant fails to provide the requested documentation, the applicant can be refused entry to Canada on this basis alone. As such, the best approach to a personal interview is to show up with all requested documentation and any other supporting documentation that you think will help the Visa officer understand your unique situation. For example, if the Visa officer is requesting information on your marital status, you should bring the requested documentation (such as a marriage certificate). You should also consider bringing with you photographs of vacations together, photographs of the wedding, letters to each other — anything that will help to show that you are indeed genuinely married.
A complete application up-front with all required documentation is usually followed by an interview waiver, although even applicants with immaculate applications are called for an interview in order to satisfy a lingering doubt that may be in the mind of the Visa officer.
The biggest downside to an interview request is the length of time it adds to an already lengthy immigration process.