1) To get top ranking in Yahoo and other directories like Dmoz ect. you should select a proper domain name. The domain name should be keyword rich because Yahoo gives more relevance to sites with keywords in their domain name.

2) Sites which are placed higher in directory structure are given more relevance than sites which are placed lower or deeper.

For example a site listed in category -
B2B/Business_Opportunities will be given more relevance than
a site listed in category -
B2B/Business_Opportunities/Directories

3) While ranking Yahoo! considers keywords in the directory structure.

For example, if someone is searching for “webhosting UK directories”, a web site listed in category - computer/Internet/webhosting_uk/directories will be given more relevance than a website listed in category - computer/Internet/webhosting_uk

4) To determine ranking Yahoo does not spider websites. It ranks web sites based on keywords in domain name, title and description. So having META tags does not make any difference to your listing.

5) DO NOT try to stuff as many keywords as possible into the description. Yahoo! editors are notorious for cutting down the description if they sense even slightest hype. Try to avoid words such as - no.1, proven, turnkey, exciting etc.

5) In the description part don’t try to stuff number of keywords. Yahoo! editors are notorious for cutting down the description if they sense even slightest hype.
Also, make sure that the heading of your home page is the same as the description you provided for your site. There should be no confusion in the mind of the editor reviewing your site.

6) The business name and the domain name must be same because yahoo use the business name as the title for your listing.

7) Content is the most vital part of the website so your website should be content rich.
This is very critical for two reasons. One - to get your site accepted by Yahoo! and Second - to maintain and get a higher listing.