Light from the front, frame at eye level, keep it plain

Three unremarkable habits produce most of the visual quality an online session needs.

Light the face from the front. The single most common visual fault is a bright window or lamp behind the speaker, which turns them into a silhouette and forces the camera to give up on the face entirely. Move the light source to the front, even if that means turning the desk around. Soft and frontal beats bright and dramatic every time, because the goal is legibility rather than atmosphere. If the only available light is overhead, something reflective at desk level in front of the speaker will lift the shadows under the eyes.

Frame at eye level and reasonably close. A camera below the speaker looks up the nose and into the ceiling; a camera far away makes a small figure in a large empty room. Raise the camera until it sits roughly level with the eyes, and frame so the head and shoulders fill a comfortable part of the picture with a little space above. Look at the camera when the point matters, at the screen the rest of the time, and do not agonise about the difference.

Keep the background plain. A background that is busy, cluttered or distracting steals attention that the session needs, and a heavily processed artificial one tends to eat the edges of the speaker's head whenever they move. A calm wall, a shelf that is tidy, a door that will stay shut: none of this is styling for its own sake. It removes the small distractions that give a divided audience an excuse to look away.