Common courtesy and an awareness of the others involved in the conference are all that is needed to make a successful videoconference.
Common courtesy is the best rule of thumb.
That isn't always the case. Additionally, be aware there is a slight delay between when you actually finish speaking and the remote sites finish hearing what you said. You need to allow a couple of extra seconds for remote sites to respond to any questions or comments you pose to the group. Additionally, the video trails the audio so that often times a person has already started speaking for a few seconds before the camera switches so that everyone can see who is speaking. It is very helpful if before each person speaks, they announce their name and the location they are participating from.