Are you ready?
Have you had hands-on practice?
Do you know how to upload your presentation? Are you sure it works? Do you know how to move/skip slides?
Do you know how to create a poll? Home many poll options have you got? Do you know how to change them? Publish the results? Move/delete them?
Do you know when your moderator is trying to tell you something in private?
Do you have a head set? Does your audio/video work?
What happens when you lose connection? What happens when you can't get in?
Remember Murphy! I see him every year in various disguise. I can assure you.
I'm in the room right now if your answer to the above is in the negative/not sure mode...
And I can ask loads more questions in addition to the above... ;)