You write your script then tape each segment and then in post production put it all together. The last step is to add narration.
Your post makes me think you are trying to do this in one shot?
Bob
I am trying to create a training video. Training material would be on the laptop in the from of power point slides. For making the video more effective, we need to be able to capture the computer screen (using a screen video recorder) along with the person (may be by useing an external camera such as webcam or handycam) and switch between trainer and computer screen as and when the trainer finds appropriate. This would help capture the trainer and his expressions as and when needed and this would help make this computer based training more effective. What are the best possible options to do so?

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