Janet Howd's Answer:
On video link audiences will either be watching you intently on a small TV screen or seeing a larger than life you projected on screen in such close-up that mere tinges of uncertainly could be seen as insecurity. If you lose concentration for example, your eyes go blank and everyone watching knows that has happened.
Under normal circumstances, a good presenter looks out for the reactions of an audience. Even when the topic of a presentation requires intense concentration the presenter 'plays' the audience assesses its reactions and aims to give its participants a good time. But on a video link there is no live audience and you get no live feedback.
A good starting point is to give you some practical experience. Set a video running and preferably with someone else watching and scoring you as well. Put yourself through as may speaking and listening scenarios as you can and give yourself marks out of ten.
Go through a number of practice runs and watch yourself like a hawk. Observe particularly closely how you look when you are doing the listening. Practice how to respond to funny questions – both the humorous and the peculiar variety – so that you know what kind of expression your face takes on at such times an can alter it if necessary.
Practice how you might react if you have not got the foggiest notion of what you had been asked by a questioner, or what caused a distance audience to fall about with laughter. Above all, be prepared to make a fool of yourself in front of yourself – this is the best way to avoid doing so in front of a live audience.