To attract more participants, you can start from some free webinars for certain times. Once you can get webinars well prepared, run webinars interactively and show the great value of your webinar, more and more participants will be willing to pay for your entire webinars and then it's a good chance to create paid webinars to monetise your expertise.
Then you ask them follow up questions to make sure they understood your presentation, what they do not understand, what objections they may have, etc. etc. You will close more sales if you are able to get feedback from clients, and Webinars allow you to see their face, to hear their voice to know how they are feeling about you, your presentation, your company and your products and services.
Urgency and scarcity are the holy grail of webinar offers. Pounce on your audience’s high energy and attention by slapping on a sense of urgency or scarcity so they will bite before their next meeting or before some social notification pops up on their screen. What you don’t want to happen is lose a sale simply because an interested prospect who planned to purchase forgot to return.