Directory Submissions are a good way and one of the simplest ways to receive inbound links to build link popularity for your site which will help your Web site rank higher in the search engines.
It is the best and easiest way of acquiring one-way links and it's almost free.
Main Benefits Of Directory Submission

• If your site is newly launched and yet to be crawled by the search engine spiders, this is the first and foremost thing that you should do.
  
• Online visibility enhancement of websites, which is why website owners employ this technique which has the potential to improve search engine rankings.
  
• Your website will be indexed regularly since your site will be found easily by crawlers
• One way links are considered more valuable than reciprocal links, hence will enhance your overall website ranking.
  
• Ability to target several keywords rather than being limited to your website title.
  Therefore, you could consider traffic as another benefit, though not as important as indexation or one way links.
  
• Links from a directory is deemed reliable by search engines because a person actually reviews the content of your site to determine its quality.
  

Mode Of Submission

• Manual & Auto Submission - Manual submission method is arguably a better submission mode as compared to the latter.
  
• However, recent research has shown that more and more cutting-edge auto submission software seems to be ready to challenge the notion that manual submission so-called a better accurate of submission method

Considerations

• Fast Submission - This is recommended for "older" sites or domains, which has been online for more than a year.
  
• Slow-Submission - You can have your website submitted to web directories but, you may delay the submission process by making it to be completed in a course of few weeks, or even few months to make it look more natural in the eyes of Google and other search engines.
  This kind of submission is usually known as SEO-Friendly submission

Tips For Effective Directory Submission

• Check if the directory has already been index by major search engines
• You may also like to also note how many pages are already indexed
• Ensure the page rank and inbound links of the directory you are submitting.
  Certainly a higher page rank and link popularity directory is the best
• If you are submitting for link building, do NOT submit to directories that uses the 'nofollow' for their site listings
• Do not just submit your niche keywords, but also include those high volume keywords as it may provide a good source of FREE web traffic