You might be used to live streaming your classes already. You might be new to it. Either way, consider having a list of exercises to hand so you can seamlessly move from one to the next. This can be out of view of the camera so it looks natural.
You can set it up so that participants' microphones are muted as they enter the class, and that you're always the main speaker (i.e. otherwise Zoom will jump to participants' cameras if they make a noise). This is a good idea in general, but especially if people are joining late and might disturb the class whilst they figure out their muting settings.
Do try a practice class before the real thing. Ask some colleagues, family members or even some of your trusted regulars to join a practice live stream and observe you. Get them to provide critical feedback on things like the position of the camera, the lighting, how loudly you’re speaking, how much you're talking, etc.
Body-weight training (or calisthenics) may now become more of a prominent feature of your live streaming workouts in the absence of standard gym equipment. You shouldn’t be afraid to go back to the basics with the classics: push-ups, squats, lunges and dips. This offers a great opportunity to focus on the mechanics of different exercises, helping people achieve good form.
As people are not in the same room as you, be prepared to explain different movements and exercises. These explanations may take the form of external or internal cues:
An external cue: direct people's attention toward the effect of their movement while executing an exercise, e.g. “push through the floor” when doing a push up or "bouncing on hot coals" when doing high knees.
An internal cue: direct people's attention toward their body and the movement process, e.g. “push through your heels” when doing a squat or "stay on the balls of your feet" when running on the spot.
The whole situation feels different, but it's also incredibly similar - people still want to exercise in a group environment, you still have to offer positive feedback, give encouragement, and provide a feeling of community during your classes. The only difference is that it's now online! Be prepared to make mistakes and know that you'll grow from the experience.
Be sure to provide people with the link (and password if necessary) to your online class. And don't leave it too late before doing so - you don't want people rushing to get into the class and turning up flustered! See the instructions to give to participants section above.