As practice, try telling a story with your b-roll and planning out a shot sequence. For example, your subject might open a door from the hallway, walk into their office space, sit down at their desk, open their laptop, and begin typing. Seems simple, right? But a shot sequence showing this 10-second scenario might consist of six or more different b-roll clips.
Footage: Think back to your audience, and the platform you’ll be publishing on and then peruse the library of footage available to you. Imagine you’re watching the footage with no text and no sound, does it elicit emotion on it’s own? Do you see a story developing? In addition to finding something dynamic, consider the look and feel of the people or environment in the video. You want to make sure that it is relatable and/or aspirational for your audience.
Professional cameras, like DSLRs, give you fine control over the manual settings of shooting video and allow you to achieve the shallow depth of field (background out of focus) that people rave about. While they're primarily used for photography, DSLRs are incredibly small, work great in low light situations, and pair with a wide range of lenses — making them perfect for video. However, DSLRs do require some training (and additional purchases) of lenses.