Inside the booth
Look toward something outside the frame
Give a portrait sequence an unseen subject.
A change of eyeline can imply a story without adding a visible prop.
Choose a direction
Keep your body comfortable and look toward a consistent point beside the lens. Start facing the camera, turn, react and return if you like. Avoid a position that hides every eye or pushes the face outside the portrait window. Make a test to establish the useful range of movement.
Keep the story open
Review the strip without supplying an explanation first. Use a short original caption if it adds something, but do not claim a real event happened outside the frame merely because the pose suggests one. Save the whole sequence so the change of attention remains visible.