Now that you've drafted a basic script, it's time to plan for the shoot. But not all of your content will be from planned shooting days. In fact, it's going to be very helpful to have extra video of the things like you working on the product, early prototypes, etc, for B-roll. B-roll is roll is supplemental footage intercut with the main shot in an interview or documentary.

It's very useful to have b-roll to cut the potential visual monotony of staring at a talking head during an interview. See the video below, which was used in Eli's Kickstarter campaign for his product Storied, for an example of b-roll. He used footage from the weeks of testing they did with an early version of the project as effective b-roll footage.