The proven way to show yourself as an expert is to write a book. You do not have to have a huge backing or go on a book tour. 
I have seen small businessmen write a book and give it out to potential customers who then, seeing (through the book) that this person knows their business, hires them.
There are virtual tours which are just as successful as the book tours that were done previously in person. 
If you check and see what the gurus are doing, they are all writing a book to show their expertise. Why reinvent the wheel? Writing a book works to show you as THE  expert.
If you are speaking on stage then you could use your book to give away (or sell) at each event where you speak. You could give it away anytime you speak to a potential client.

Bottom Line: Name recognition through your book will increase your client list. That is why the gurus are giving their books away, which also increases their mailing lists.

I work with authors all the time and name recognition is pure gold. Writing a book is how it happens.