As someone who has made this transition, it's too long for this answer box. I did, however, make a website about it: http://webinarhow.to.
Briefly, in the long term, you've got to shift your mindset from a service model to a products model.
In the short term, you need to do more marketing, more blogging, more emailing, more partnerships. Work on getting a bigger list.
I've successfully moved from the clients/service model to the webinar/products model and if done properly, it's a much more reliable stream of income.