There are many free or low costs things you can do:
Marketing on Facebook or Linkedin (depends on what you offer)
Contests
Influencers
Killing testimonials
Pick up the freaking and make phone calls (you have to learn sales. Any business is 90% sales).
Sales is scary but there are lots of easy ways to do it, that gives you confidence.

Give me a buzz to set up a killing strategy that pays.

It's been my experience that the only way to build a huge, engaged, and paying audience is by building your email list.

If you're starting from zero I recommend you allow for your social network (friends, colleagues, etc) to help you tighten your web based services first. What I mean is to sell, and generate buzz by not selling at all. I'm in the midst of doing it right now. I'm productizing my book. Creating a Fedora based 7 week course with video tutorials. I'll seed my list first with an inquiry. So perhaps 200 people on my Facebook page see the announcement. I will ask them for feedback. I'm launching this product, and I'm very excited about it. What 2 or three things would you like to see in my course that perhaps I've overlooked? Now your community is engaged, and helping you. You should institute some manner to aggregate more emails to your email list when people land on your site. I recommend SUMOME. Simple, and easy to integrate to nearly any email service. So as they register with you, the email automatically passes to your provider.

Dr. Robert Cialdini speaks in great detail how this whole sales process unfolds. Law of reciprocity, authority etc. Now they've helped you tighten your web based service. Now you should thank them. When you thank them, you can give them a coupon to gain access to your web based service at a lower rate. Now comes the fun part. List this MVP version of your services available for a short time (24 hours). Once that's up the sale will close. End. Forever.

1. You engage your audience.
2. You aggregate emails.
3. You generate buzz.
4. You take constructive feedback and improve your product (remove the guess work).
5. You launch your MVP.
6. You offer something that nobody else gets (rewarding your insider friends and family).
7. You close a date around purchase.

While this may not get you 20,000 customers, you will certainly be on your way.

Most important take aways:

1. BUILD AN EMAIL LIST.
2. ENGAGE YOUR AUDIENCE IN YOUR PRODUCT.
3. GIVE THEM SOMETHING TO TALK ABOUT.
4. LIMIT THE ON SALE TIME.

Happy building.

Learn everything you can about what's now being called "growth hacking."

1. First, its all about the product. Create a minimum viable product (MVP) -- like a prototype -- and then present it to potential customers. Ask what they like, what they don't like, what they'd like to see, whether they'd pay for it, and how much they'd pay. You want to establish a perfect product-market fit so that it sells itself.

2. Integrate marketing into the product. Hotmail added a signup link into the footer of everyone's e-mail. Dropbox and other SaaS products offer referral bonuses to users.

3. Experiment with different marketing strategies to see what brings the most users at the lowest cost. Spend a little money on online ads, PR, and every other tactic to see what works the best. Once you see what delivers the best ROI, then pour all your money into that tactic.

Good luck! Let me know if you'd like to talk further.

PS -- I'm doing exactly this in my role as Director of Marcom at a high-tech startup.

Webinars! Check out a company called LeadPages.net. They have been killing it in this arena by using weekly webinars to engage, educate, introduce and offer their software to attendees.

In fact, they recently taught a strategy on how you can do webinars for free (without paying the costs of using, say, a GoToWebinar software):

1 - The formula involves setting up a Google Hangout (google.com/hangout). Set the webinar for "later."
2 - Get a chat feature embedded (i.e., http://chatango.com)
3 - Create a page to host your hangout (I suggest using one of the LeadPages pre-made templates)

I've seen webinar marketing work in almost any industry. It's nice because people feel like they've spent time with you but it's scaleable for you, the business owner/marketing director, because you can have many people there at once.

Also, the idea of appointment marketing works well. And it's not surprise that Fortune 500 companies use this as the #1 sales mechanism to drive more sales.

LeadPages has a whole free course on webinar marketing. If anything I've written above interests you, then I'd definitely recommend you check it out: http://www.leadpages.net/webinarfunnel

To get 20k users to your booking site follow the following rules:
1. Contribute to other sites: Bloggers consistently use guest posting as a method of obtaining valuable back links to their blogs. This method is so useful that it evolved into content marketing, a popular method of digital marketing. By contributing to other sites, whether as a guest poster or simply a source for an article, you will raise exposure for both you and your brand. Referral traffic is raised, and search engines give better rankings for sites with backlinks from reputable sites. This makes contributing to other sites one of the best, across-the-board digital marketing techniques to raise traffic to any website.
2. Rank for long-tail keywords: While some keywords gain a lot of traffic, the large majority (70 percent, to be exact) of online searches are long-tail keyword searches. For example, instead of searching for “bicycle,” I’d likely search for “mountain bikes under $500.” Organic search traffic is the holy grail of Internet traffic, as it is automatic and sustainable. Optimize your website for broad keywords, but also include as much niche detail as possible. Blogs help create landing pages to answer specific questions and provide specific information for as many long-tail keywords as possible. By starting a blog, you exponentially increase your odds of being found by qualified leads for your business.
3. Drive referral traffic: Organic search is important, but so is referral traffic. Guest posting isn’t the only way to generate referral traffic either. Social media sites like LinkedIn, Facebook, Twitter, Instagram, Snap Chat, and StumbleUpon can help drive referral traffic to your website quickly. Social signals can also help raise search engine traffic.
4. Consistently create content: It takes consistent content to drive traffic. While you may eventually accumulate 100,000 views on a single post, you will need tons of posts for the daily volume to make a difference. Research from HubSpot shows companies that publish at least 16 posts per month on a consistent basis gain more traffic than those who do not blog or rarely add new content. Even blogging every day, it can take months to finally craft a post that hits and drives massive amounts of traffic. These tent poles support your efforts on smaller projects. You will need 400 or more blogs to generate sustainable traffic, which will take over a year of blogging every day.
5. Sustaining your following: Even when you gain 20,000 followers, they will not last unless you keep hustling. You will still need to take steps to keep the content fresh. Adding images and videos, updating content with newly discovered information, optimizing your site for speed, and continuing to promote your brand on social media channels all contribute to keeping your site at the top of the search results. If your site has valuable information, it is likely to be cited by other sources. People will tell their friends about you, and your brand awareness grows. All of this helps sustain your site’s traffic. Anyone can draw eyes but keeping people happy takes attention to detail and a focus on delivering consistent quality.
Besides if you do have any questions give me a call: https://clarity.fm/joy-brotonath