Knowing how to find what you are looking for is the underlying premise of SEO. Link building requires diversity, but not all links are created equal; which leads to the next point.
In order to separate the wanna-be directories from the real powerhouse domains, you will need to understand how to search for them, and when searching for anything, it doesn’t get any better than using Google.
This is why we would like to direct your attention to a post from the past covering search tactics and the use of Google search operators using a wildcard method, that allows you to find authoritative directories to build links easily.
The post is amply named: SEO Tips for Link Building and Directory Submissions has a few great tactics than anyone can employ to find authoritative niche directories with ease.