Right Frequency of submission to Directories 

New Domain (New domains also include the sites that have a few back links and the sites that have been in search engines results for 3 months or less)	First week - max 8-10 directories per day Next 7-10 days - max 15 directories per day Rest time - 10-15 directories per day When the dorectories list comes to the end you should better add to max directories per day during the last 10 days
Standard Domain (The sites that are less than 1 year old, display in search engine results, have some back links and indexed pages)	The best way is to start adding to directories with a high Page Rank: First week - 15-20 directories per day Next weeks - 10-15 directories per day
Old Domain (The sites that are older than 2 years, have been more than 1-2 years in search engines, have the internal pages indexed, have back links from pages with PR3 or higher)	There are no special rules. It's enough to add the site on a consistent basis. It's recommended to submit to minimum 15 directories per day. When the directories list comes to the end the best way is to add to max 7-10 directories per day during the last 7 days.