Linking is basic; you get as many people as possible to link to you, and you link to whoever you want to link to. You can never have enough one way links. The more directories that link to you, the better it is for you. Most SEO consultants submit to hundreds of directories, and there are free resources that can help you (in a semi automated fashion) submit to thousands of websites. Any software that guarantees full automation is probably lying, since most directories now use graphical images (captcha) to verify whether the entries are being made by humans.
You should always keep it in mind that you are doing directory submissions in order to increase your back link count. Note that search engines consider links from directories to be very good, since the links have been vetted by the human editors on the directory.
Yahoo Directory Express charge an exorbitant $299 a year, and there is no guarantee that you will rank highly on Yahoo's SERPs anyway. I believe this directory should be done last (if you want to be listed on it at all). This is a paid directory, as are most top directories apart from DMOZ.
Submit helper also has lists of niche directories and paid directories. If your budget covers it, submit to every single directory that will have you (including any niche directory in your specialty). Niche directories are especially good at bringing in targeted traffic. This is good because it ensures that only traffic which has been searching for your site via going through the directories will get there. Some good directories for sites that sell online medications.
Paid directory submissions versus free directory submission
When it comes to links, I will take volume over quality any day. Get all the free links you can, then start paying for paid directories from highest to lowest cost. You always have to look at it from a cost benefit basis, and a lot depends on the size of your budget. A few hundred directories charge less than $15 a year, while several others charge almost $300. However you look at it, it pays to "go with the free."
SEO Directory submissions
Submitting your URL to directories is the beginning of your linking program. It is the easiest way to start and an assured way of getting non-reciprocal one way links. After this you can start actively link trading (which is like dating). Hopefully you would have a backbone of several hundred backlinks and an appreciable PR before you start reciprocal linking. Also check out our article submission service.
1. Why Directory Submission Service?
2. When Use Directory Submission Service?
3. Yahoo Unveils Search Assist Improve SERP with Article Submission Service