Send them invites for your webinars or whitepapers. Send an email regarding it, and wait for their response on it.
? Select the appropriate day and time for hosting a webinar:
page. Use your company profile to promote this by updating statuses related to it.
? Webinar helps generate a massive following for your brand, and Google+ enables you to host on hangout for free.
Try to attract customers by offering them something in return for registering and attending your webinar. You can run a contest related to the webinar using social media.
The tips above help easily market your webinar through various social media platforms.