Now, "every" Internet marketers is doing his own webinars. Unfortunately, this is nearly always to sell you something and not really to teach you something even if they claim you will learn this or that.
If you subscribe to a few mailing-lists of Internet marketers you will receive their emails to inform you about their latest webinars. You will be able to see how and what they are doing.
In most cases these webinars are free as they are made to sell you something inside.