This idea of expertise and authority can apply to any field or business. Say you're a hairdresser in Adelaide, and you have a website for your salon. You may have added your URL to relevant directories, classifieds, etc. But then what? Well, you can definitely improve your SEO substantially by expounding your expertise in different ways online.
Keeping your own blog (and writing guest posts for other blogs) is the obvious way to build your authority. This is not only because you can keep adding insightful, expert information to it; but also because if your blog is part of your main domain you increase the odds of getting links directly to it.
While a blog is preferable, you can get a similar effect by building authority on Twitter. If you constantly link to interesting articles and blog posts (by yourself and others) as well as tweet quality tips and insights then you will definitely develop a reputation as someone who really knows her stuff. Links to the URL you include in your profile are sure to result after a while.
Of course blogging and Twitter are mainly about words, so they're great for people who love to write. But what if you're not this way inclined? There must be a lot of people in this boat; people who have much useful and detailed knowledge about a subject, skill, or profession, but just don't enjoy working for hours on a PC keyboard.
If you are one of these people then YouTube could well be the go. There are countless people who have built substantial followings on that site simply by sitting in front of a video camera in their homes and telling -- or better still showing -- viewers how to do stuff.
Deliver interesting, insightful and most of all useful tips, advice and observations in your videos and people will have no doubt that you really know your stuff. Some are sure to share it on social media. As long as you feature your URL in your visual offerings some sturdy dofollow backlinks will result eventually.