Try to make sure that a large, soft light (rather than a point light like the sun-with-no-clouds) is in front of you (rather than behind you).
Somewhere between “10 o’clock” and “2 o’clock” if “12:00” is where the camera is located. So, if your head is the center of a clock, and the phone camera is 12 o'clock, then stand about 2 ft away from a window that is either at your 10 o'clock, or your 2 o'clock
Record horizontally
Frame yourself to allow for a little headroom
Keep phone lens at eye level
Hold the camera steady, or, better yet, try to stabilize it by leaning it against something or clamping it to something.
When you "look up at the camera" look into the lens, not at the screen.
Stay close to the phone so that you pick up good audio.