If you have implemented changes all over your website, eliminated duplicate content or had to deal with a malware attack on your site and you have now fully cleaned it up; then these are all reasons for you to try and get the Google bot to re-crawl your site. You will get rankings increased faster and new sections of your site will be identified on your website but the question is how effective are the current methods of doing this?
The usual process of XML sitemaps being resubmitted or using a Ping service are all parts of hit and miss methods to get Google to re-crawl the site.
Now Google Webmaster Tools have introduced a new method which is called “Submit URL to index” and it is official by Google, so no more hoping that they will index your site today or tomorrow or even next week!
They have quoted that they will usually re-crawl the submitted URLs within a day thus you getting nearly immediate indexing results for your website.