Always completely charge the batteries for your camcorder or your mobile phone and have extra batteries on hand, if necessary.
Pay attention to clear, non-diffuse light while shooting.
Avoid creating shadows in your shots.
Pay attention to clear sound, especially to wind noise or permanent sources of sound such as air-conditioners, street noise or other sources of disturbance.
If you are filming with your mobile phone, you should get as close to the object as possible so that you can record the sound well. If you are too far away, you can't hear much of anything.
While recording, count backwards from 3 to zero. This guarantees that you have enough material to blend later when cutting and that the beginning of the shot isn't cut off.
Pay attention to the camera work - it's best to film with both hands or to use a one-legged tripod, if necessary. This makes for smooth shots.
Take your time with your shots, do several takes of one scene and check the recording already on site if you can.
During pans or zooms, try to maintain a constant speed. This is necessary to ensure that when you cut and splice your raw material later, you can give your film a certain flow.
When including additional material such as charts and diagrams, be careful to present them in an easy-to-understand way. This makes them highly suitable to emphasizing your message.
And last but not least: Always turn on your camera :-P