Show, don't tell. It's the storyteller's mantra, but it sure applies to microlearning videos, too.
Avoid long stretches of time where nothing is happening on-screen while the host speaks in the background.
In a tutorial video, the amount of time spent showing the learner how to do something should be maximized, and the amount of audio-only commentary minimized.
If you're creating a video of a conversation, use cuts and framing to add greater realism and visual interest.
For conceptual videos, get creative! Tools like PowToon and VideoScribe are making it easier to illustrate your points with graphics and animation.