First of all, you should consider starting promoting the webinar 2 to 4 weeks before the delivery date. If it's sooner, you won't have enough time, if it's earlier, the impact will be diminished, since people generally need a sense of urgency in order to act on an offer.

So here are some tips and tricks on how to promote and market your webinar or webcast:

1. Publish your webinar on your blog or website

This is the first natural step. Even if you use an event management website (such as BrightTalk or EventBrite), publish it on your website or blog as well.

2. Optimize your webinar page for search engines (SEO)

Use keywords in the webinar title (however, don't go overboard and have a 4 line title), in the first paragraph, in links and headlines. It's also useful to make your keywords bold. Limit yourself to 4 or 5 keywords because, if there are too many keywords, your page relevance for each keywords diminishes. It's also advised not to repeat a single keyword more than 4 times on a page, it can be considered keyword spam if you do.

3. Send a press release

If you don't want to pay $80 to $360 to PRWeb.com, there are many sites that publish press releases for free. You can find here a list of 50 press release submission website. Don't forget advice #2 when writing the press release.

4. Send a newsletter

If you have a subscribers list, don't be afraid to use it. If you don't, go to the next advice.

5. Use social media to promote it

Publish your webinar or online event on Facebook and LinkedIn (they allow events posting) and invite people from your network to your event. Post regular updates in Twitter. Post your webinar on forums in that particular field. This is a sensitive topic, you need to be a regular member and post frequently on those forums, otherwise you might be treated as a spammer. Post it on digg, reddit or StumbleUpon.

6. Publish it on website that promote webinars

There are lots of websites that promote webinars and other online events.

7. Create partnerships

Give a discounts or a number of free spots to a partner website's members in exchange for promoting your webinar or web conference. Do cross promotions: you promote your partners' products (books, online events or even webinars), they promote your webinars.

8. Notify your contacts

Send them an email or, better yet, place a link to the webinar in your email signature. It's a good way to advertise a product to your contacts without being intrusive. They might just be interested in your webinar or recommend it to someone else who is interested.

9. Publish a video teaser on YouTube

YouTube is being used more and more as a search engine. It's well indexed by Google (actually, it belongs to Google) and will help you get more visibility.

10. Start a contest

In order to generate interest (and even quality links) you can start a contest, offering either a free spot, a free product or service or anything else you thing others might value.

11. Paid advertising

And the last resort, pay for advertising:). You might use some PPC (pay per click) advertising networks such as Google AdWords.

Webinar Base lists the most interesting free webinars, webcasts, web conferences and online courses on different topics, from social media, sales, business, to real estate or design.