Your blog is always automatically crawled by search engines every time when you publish or update a blog post. But if you want instant blog crawling, you can ping your blog for update search engines to tell about new post or post updates. Sharing your post on social media sites like Facebook, Twitter, Google+ etc is also good way to promote your (new) blog post.
When you use a ping service it send information regarding a new post or post update on your blog to all search engines including Google, Bing, Yahoo, Google blog search, Weblogs, Feedburner, Blo.gs, Icerocket etc.
Hereunder few popular free ping services are given –
Popular Ping Services
How to Ping?
All ping services ask for your blog title, blog url and feed url (xml or rss). Some of these may ask for more than one links and short description about new updates.
If you have published a new blog post then it is very good to use a ping service. But to ping a non-updated blog again and again is considered as a Spam so be aware of that. It might hurt your next crawling.
Pinging might help you to maximize your blog reach via search engines to gain new audience.