Have a script handy
For an experienced teacher, this may not seem necessary, but really it is. Even if you are presenting a lesson that you know well and have taught many times, it is important to have some notes already written. Teaching by video conference is not the same as teaching in the classroom. The thought that your image is being beamed to people in a remote location may make you more nervous than you'd imagine. Whether you take a lecture-style approach or involve your class a lot, you feed off of listener reaction and participation. This is true no matter what the reaction is-even looks of boredom. When you are presenting a video conference you do not get that same type of instant feedback.
Give a shorter presentation
If you thought a student's attention span was short in a typical classroom setting, wait until you see how they fare during a video conference. Some will be fine, but others will get fidgety fast. If possible, do not spend the entire class time talking. Just as you would in any other class, give students time to do a group activity. Or let them swap and grade each others' papers while you go over the answers. Find a way to break the time up, so students are not looking at the screen the entire time.