1. Work in a niche.
2. Be the best in your niche.
But seriously, try to focus on one industry and pursue clients. Tell them why you know their business better and get them results. The rest is easy.
For example, if you are in the plumbing industry, say “you don’t need just any seo expert – you need a plumbing expert who does seo”. Of course you need the know the product/service inside out. Where SEO is going, it’s all about good content, relevant keywords, and a great web experience. A bunch of backlinks and other manipulations won’t get you as far as they used to.