Whether developing a 200-hour technical training course, a 3-minute marketing video, or a new corporate logo, the preparation is essentially the same. Of course, if the project budget, schedule, or technical requirements allow or require it, this planning process can take months, instead of days or even hours. But the basic prep activities should not change. Be prepared to gather the following information at the start of every job.

WHY video, print, web and other communications can benefit from interviews.  

And HOW to assure you will get the personal content you need.
 
Nothing so animates writing as someone telling what he thinks or what he does – in his own words. His own words will always be better than your words, even if you are the most elegant stylist in the land. (William K. Zinsser, On Writing Well, New York: HarperCollins Publishers, 1998: p100)