Do you have a clearly defined target audience? If so, great! If not, that would be the first place to start.

Second, where does your target audience hang out, online and off line? Be specific and create some lead generation strategies to reach them with a call to action.

Hope that helps.

Such a competitive market. You need to know exactly who you want as an ideal client. Then that is where you need to market. Some options are local associations and other services who already sell non-competing services to the same people.

This depends on what you're currently doing. There's the old school tried and true methods of cold calling, direct mail, and networking. There's also digital marketing, where you can leverage your skillset in SEO to attract local traffic. Also, there is paid search and social marketing.

The best method with the highest close rate would be leveraging your existing network. Let everyone know you do web design, development, and SEO and that you're seeking clients.

First,Go to where the need is the largest. Understand what is driving that real need. Define that target audience and employ your solution. Stop using a shot gun to hit the target and use your revolver.
Second, Design yourself a workable 6 step sales cycle process Suspect, Prospect, Education, Proposal, Negotiation and Close.
Lastly, Keep a active flowing sales pipeline.
We will support you on all levels.
Mims Morning Meeting LLC

Do inbound marketing.

Or, outbound/direct marketing.

Those are basically your options. :)

Since your question is so broad, it's tough to be more helpful than that. But as square one, I'd define a narrower beachhead market. Web design, development, and SEO are huge disciplines, each with many smaller disciplines beneath them, and quirks for various markets beneath that.

Currently, based on searching LinkedIn for companies that also offer that stuff independent of geography, you have 10's of millions of competitors. By refining to be more niche, you could easily lower that to 10's, which is usually a great, early move for any business. It can always grow more broad later.