Many of these users expect the Event page to be like a television station - there's something always playing, but they're show will start at the advertised time. To help educate visitors, I created this video which I place in my Event's YouTube URL:
Now the visitors know to tune in at the scheduled time to see the live HOA.
Other things you could do:
- create a "commercial" with your participants that will explain what they can expect when they tune in at the proper time
- run a related video
- run a cartoon or movie
- run your favourite music video
If you want to create your own video, one of the easiest ways is to use YouTube's Slideshow tool. You can create slides in your favourite graphics editor (or PowerPoint), save them as files and upload them. (Tip: use music from YouTube's library so your video won't get pulled for infringement). Or create something in a movie editor and upload.
Easier still, just link to the video I created and paste it into your Event!
For more information be sure to read Clearing up the Confusion of Google Events and Hangouts on Air (HOAs).