Using a script is one of the most underrated best practices when it comes to speaking to your students via a recording. You may be very comfortable talking to your students in a live classroom environment, but may not be as accustomed to just you and a video camera. Try writing up a script or at least an outline of what you want to say.
It can be more than a little embarrassing to have yourself repeating the verbal debris “um” over and over in a video you are planning to use in classes. A script minimizes the chances that you will forget the point you were trying to get across to your students.
If you do your recording in a studio, you may have access to a teleprompter right in the camera. That way the students don’t know you are reading your script while you look straight at them. There are also great teleprompter apps for your iOS or Android device.
At the very least just writing yourself something up in word or on a note-card can go along way toward smoothing out your presentation.