If you have a well developed storyboard and script, planned your props, location and scene details, the filming process should go smoothly.
Actor
Look at the camera.
Speak loud enough and slow enough so that your audience can hear and understand you
Hold our interest - don't be boring, be interesting
If you make a mistake, pause and continue - we can edit stuff out!
Try to minimize fast movements
Know your subject matter
Have fun - relax
Director
Know the storyboard and script
Help the actor relax
Keep project moving towards completion
Minimize distractions and outside noise
Stay on task
If things aren't working - suggest making a change or reshooting
Camera Person
Review the storyboard
Walk closer to zoom in
Stay close enough so that audio can be recorded
Keep the camera rolling - it is easier to edit out what is not necessary
Keep the camera steady
Review some of the video footage to make sure audio and light look great
Offer suggestions for improvement - as you can "see" what it looks like on camera