If you do what you preach, you have probably optimized your own website to a top-notch inbound lead generation machine already! However, if that is not enough, here are a few ideas:

1. Register to some of the big sites where projects are offered. Like Clarity. :) Freelancer.com is a big one as well, with a lot of SEO projects available.

2. Paid advertising. Do it well or it will cost you more than it brings in.

3. Find web sites where you can meet the future clients: business sites like LinkedIn or some more SEO specific sites like SEOChat for example. Search them for posts with a stated need for SEO company.

4. Also, define your target group well. When you know their pain points, you can address them directly.

Good luck with your new company!