Try to make a convincing invitation to drive registration. Don't give them a reason to feel like your invitation is a corporate "fill in the blank" form. Target a specific segment and make a personal connection, so you can retain them longer.
Hold a customer survey via email to learn if your previous customers are satisfied. The referrals generated by these customers proves to be solid leads, because they come from a customer who already has experienced your services and products.
Webinar handouts offer the ability to share content directly to the attendees and absentees before and after the webinar.
It is really difficult to get an audience to be a part of your webinar. You always need to look for a topic from your niche that is trending to be able to capture the attention of a large audience. Do some research and look for customer problems. Be relevant and informative with your webinar topic to encourage more people to attend your webinar.