Start with what is important technically
You want to look professional/like you know what you’re doing. Try to eliminate anything that is distracting and put yourself to best advantage. Start by checking where you are on the screen. Place yourself in the centre, with only a fairly small proportion of the visible space above your head so you are taking up about a third of the screen. So often people seem huddled down the bottom of their picture, or slouching off to the side. It can be very off-putting.
Make sure your camera is at eye level or just above.
Lighting: make sure you are well lit. Keep a window and/or light in front of you, behind the screen and on your face. Can people see your face clearly? Lighting from above can be rather harsh and if the lighting is from behind you’ll be in silhouette. You might want to add some soft side lights, but the main thing is to ensure people do not have to strain to see you.
Background. Is your background more interesting than you? Try to make it neutral if you can. You want the attention on you, not on your bookcase, your interesting row of Mexican masks or a heap of old washing. Above all, do not be upstaged by what is behind you.
Can you be heard easily? Make sure your microphone is picking up your voice sufficiently. Laptops and so on differ enormously in how well they pick up sound. And if you are sitting away from your machine it might mean others are struggling to hear you. You can always use headphones with built-in mics or get yourself an inexpensive clip-on mic. Webcams are also inexpensive and give you a great picture and their built-in mics are often just what you need
Speak to the camera as if you are addressing one friendly person that you want to tell or explain something to.
Don’t rush. People need a little longer to take in what you are saying.
Vary your voice. Think of it like music, which changes pitch, intensity, pace. Music that stays on the same 3 or 4 notes in the same rhythm is very boring!
Where to look? When you are addressing a group you have two options about where to look. Looking straight into your camera lens makes your viewers feel you are looking straight at them. You wouldn’t want to do this all the time as it would be tiring for you and for your audience. If you are in gallery view you can look around your audience and they get the same feeling as if you were standing on a stage looking round a live audience. It’s fine to look away to picture things in your mind’s eye or to look at notes too. Variety is the rule here too really.
And remember: If you are looking down at a laptop screen – they are looking up your nose!
Practise and check. The useful thing about online video meetings is that you can go online before the meeting or event and check how you are looking. Always check your hair, glasses, clothes before you go live online in case any need adjusting. If you are speaking at something, then practising and recording yourself in advance is really useful.