Webinars are fairly popular, but the direct return on the investment of hosting a webinar is sometimes hard to determine, especially if you're a startup. To paraphrase a biblical quote, "Many are hosted... but few make money."

So I was surprised when Clément Delangue, head of marketing at Mention, told me they made $10,000 in just the first two hours after their initial webinar. (I included Mention, a tool for monitoring your brand's presence on the web, in my list of 8 Powerful Social Media Marketing Tools for Savvy Businesses.)

I asked Clément how they made their first webinar such a success:

1. Optimize your landing Page with Unbounce. The number of people you get to sign up for the webinar (whether they can make it or not) makes a huge difference. At the very least those who missed the webinar will get a video recording of the event, which is also a great tool for retention and answering frequently asked customer questions. So it makes sense to optimize all the steps of the registration funnel, including the landing page you create to allow people sign up.

With Unbounce, plugged to GoToWebinar through Zapier, Mention managed to initially get a 53 percent conversion rate on their landing page (that they grew later to 63 percent), which resulted in over 800 signups for their first webinar.

2. Get new users signed up every day. Mention is used by over 150,000 clients so they have extensive engagement with their users, whether for commercial or support reasons. Simply adding an invite link to the webinar on the bottom of their email signatures, and setting up automatic messages through Intercom, helped them build momentum and increase the number of people who signed up every day... and in the process increased the buzz about the webinar.

3. Create an alert and answer every question on social media during the webinar. A webinar should be a means of answering as many user questions as possible, so Mention dedicated two members of their team to answering questions.

Then they leveraged those efforts by asking people to put what turned out to be over 500 questions not only on GoToWebinar but on social networks, too. Thanks to an alert created on Mention (why wouldn't they use their own tool?) they were also able to live-track the over 300 references to the webinar  posted to social networks.

4. Offer a temporary promo code at the end. Once you've answered all the questions coming in it's time to close the deal. By offering a 30 percent promo code that only lasted two hours, Mention signed up 10 percent of the attendees to a premium plan, generating a $10K return on investment. They also saw a spike in social activity and viral buzz and a significant decrease in common support questions in the days that followed.

Plus, by sending out the video recording and breaking up the webinar into useful chunks for support, the webinar has become a lasting tool that drives adoption, user retention, and awareness of best practices--all from one live event.

Those are Clément's tricks to make your webinar worth it. Hit him up on Twitter @clementdelangue for more.