A few things will help you get successfully listed in major online directories. Forget them not!

Title

When asked to provide a title for your site the best title to choose should be simple and to the point. Do not try to use search engine friendly anchor words unless the directory guidelines give you the ok. The last thing a directory owner wants is 50 sites listed under one category with the same title. If all else fails use your URL without the http://www portion (eg. YourSite or yoursite.com)

Description

Your description should accurately describe your site. Avoid keyword stuffing. Keep it clean and to the point.

URL

Always give the direct path to your URL. Most directories will reject URLs that redirect. Also, avoid affiliate links.

Category

Search the directory to find the best possible category for your site before submitting. I've seen many directories that simply delete submissions that are in the wrong category. If you can't find one that suites your sites topic either request a new topic (If the directory allows this), contact an editor and ask them for the appropriate category or submit your site to the category which best fits.

Submit and Forget

Popular directories are usually plastered with submissions on a daily bases. Its best to submit your site then move one. Nagging the editors usually will get your site rejected. If after a reasonable amount of time say six months you site is not listed then contact them unless there guidelines forbid it.

Appearance

Double check your site before submitting. Make sure it looks clean, there are no broken links or under construction signs. It's also wise to view your site with different browsers to make sure everything looks ok.

Make sure your site actually has content on it. The last thing you want is for an editor to click a link and it goes to a page with a header, some ads and nothing else.

Get help from a professional for directory submission. They will guide you through it and will generate 90% success rates.