half of a genuine conversation between two people which is far more natural and relaxed than a "talking head" and two, you don't have to remember your lines in anything like the same detail. All it needs is for someone to sit beside the camera (or it can be the person running the camera, depending on whether you use remote control or not) and ask you questions which you will have pre-agreed, but not over-rehearsed. You then look at the person (so your eyeline ends just to one side of the camera) and reply to him or her. The person's questions can then be cut out afterwards, or if you really like the "fly-on-the-wall" approach, you can leave them in. Whoever asks the questions must take care not to phrase them in such a way that you automatically respond with either a "yes" or a "no" as this can make the dialogue fall rather flat. The way to avoid that is to ask "open" questions and these are what journalists use -- start every question with: what who where why when which ow etc. And finally, leave a short gap between the question and your answer so that if you decide to edit out the questions later, it can be done cleanly. Similarly, don't talk over each other as that can mess up the soundtrack. Another damning element of some amateur videos can be that the voice of the speaker sounds like s/he was talking from the bottom of a