Audio should be consistently audible throughout your video.
Many video and audio editing programs (like Camtasia Studio and Camtasia for Mac) allow you to "normalize" the audio in your video. Normalizing your audio basically means that your audio levels, how loud the audio is, will be set at the same level throughout your video making it easy to hear.
Your primary audio (instructional content) should be distinct from other audio within your video.
If you add music or sound effects to your video, set the audio levels (the loudness) so your primary audio is easy to hear over the secondary audio.
Edit out dead air and avoid or eliminate "ums," "uhs," filler words and long pauses.
Long pauses in video and audio are distracting and provide your viewers an opportunity to abandon your video--edit this out of your timeline.
Lighting your video properly is the easiest way to make your videos look more professional.
Use the preview window on your camera or computer to check the lighting of your video. When shooting video with people, be sure faces are fully lit and that there are no shadows.
The subject(s) of your video should be in focus and well framed.
Whether you use a webcam or another video camera, make sure the subject of your video is clear and in focus.
Your video footage should be stable, not shaky.
Use a tripod or other attachment to ensure your video footage is steady.
Proofread titles and text.
Proofread all text in your video. If you use Powerpoint as part of your video, run spellcheck before recording your video.
When screen recording, consider everything your students will see on the screen.
Clearing off your desktop and using a subdued, solid color as your background is less confusing for viewers. Also, when showing a screen recording in Blackboard, be sure you're in view mode, not edit mode, so you do not confuse your students.