It is very important to add your blog site map to webmaster central rather than you are adding to the directory.The site maps are used by the search engines to find,index and rank your site.
To submit a site map to Google you need an webmaster Profile.You can create a webmaster profile by visiting the page http://google.com/webmasters once you are created a webmaster profile you can proceed to the submission of site map.
Before submitting your site map you have to verify your site with Google webmasters.Google uses two methods to verify the site one is meta tag method and the other is by uploading a file to server.If you are using blogger it will be easy to do a meta tag and if hosted WordPress you can go for any method.
To verify a blogger blog copy the meta tag and paste it between <head> and </head> section of your blog and click on the verify button.
If you are an hosted WordPress blogger you can do the same what we did in the above for blogger by editing header.php or you can upload the file by FTP at the root of your blog.
After you are verified the site,your site will be appeared in the sites list.Click on the site URL there and in the left side bar click on the Site Configuration
A drop down will come and click on the Site maps.In the appeared window you can see a button named “Submit a Site map” Click on it will ask you to enter your site map.
If you are a blogger user then in the appeared box enter that atom.xml or rss.xml then you can press submit site map.
If you are a WordPress user you have to create a site map first you can go through http://moretricks.com/create-sitemap-for-wordpress to create a site map for WordPress.
Once you are created the site map you can enter sitemap.xml on that box and click submit.
Now you can log in to your webmaster central to know crawling details of your blog.Hope you successfully submitted your sitemap to Google webmasters