Manually going into directories, searching page structure, positioning , and the presence of no-follow indicators, will exhaust the average webmaster. And even when you find a great directory to list your site in, you still may have to pay for an editorial review of your site. And then you have to wait to see if you get accepted. If you are dealing with free directories, then you often times have to wait even longer to see if you get accepted. Additionally, you need to develop a system that allows you to track your submission to directories to follow up on the rate of of acceptances and denials. All of this eats tons of time, and delays the crawling of links leading to your sites. On of the easiest ways to find directories yourself is to go into Google and type add url followed by your keyword and the word directories. Or you can do this same search by using add link with your keywords. Often times, building a relationship with other webmasters in your niche is a good idea for placing appropriate link on each other sites. This personal relationship will facilitatethe proper placement of your links and help you get them approved much more quickly. However for most people who want to see quick results, and don't have much time to be a social butterfly on the internet, some type of paid directory that guarantees placement is the way to go.