Make sure that you set up your shots with adequate lighting. It is great to get footage outdoors during the daylight but if you are shooting something indoors, try to make sure there is as much lighting as possible. Try also get your subject to speak close to the camera’s microphone as possible.
Lastly, do not center all of your shots. The same rule that applies to photography can also be applied to videography. It is also called “the rule of thirds”. This is when you divide the shot up like a tic-tac-toe board and place your subject in any of the windows, except for the center one. See the example below: