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In some cases it will be necessary to show your video (webcam) in the meeting. This can be your built-in cam or an external device, it doesnt make any difference. However, sometimes these devices have a built-in microphone as well, which isn't useful in this context. Be sure to set that microphone to 'off' or 'mute' in your operating system's audio settings.
Network
You should accessing online meetings using a wired ethernet connection, these applications are demanding on the network and the packet drop can be high over WiFi and you will tend to experience lag, dropped audio and other connection problems. If at all possible, you should use a wired connection, especially if you are hosting the webinar or chairing the meeting.
Environment
Lastly, your environment should be reasonably quiet, comfortable and have a ready supply of coffee.