Be an Authority in your domain

A strong marketing advantage to be considered as an authority in your niche or domain.
This will allow you to increase your rates and encourage more potential clients to contact you rather than your reaching out to contact them

You can brand yourself as a domain expert in a variety of ways: 

• Start a blog: This would demonstrate your knowledge and skills to potential clients and give them insight into best practices in your niche. You could also include case studies on how to have successful client engagements. 
• Write an ebook: You could write an ebook about your niche. This will demonstrate your knowledge and ability to write well as well as the depth of your knowledge in your field. Plus it takes dedication and commitment to write a good ebook. Who better to engage as a freelancer? 
• Answer Questions: Join and engage with the forums and sites that are a focus of your industry. Stack Overflow for coders, Reddit and Quora are also good platforms. 
• Get involved in discussions  – Joining discussions and communities in your domain
  • Facebook groups
  • Twitter conversations
  • Podcasts
• Start a youtube channel on your area of expertise

Each of these will require time and effort to be involved in but if you focus on one or 2 initially until you get some momentum you will then find time and material for some of the others.
The aim remains to have your potential clients and their network think of you as the go-to person for your area of expertise.