XML Sitemaps are a great way to provide a complete list of your webpages to Google for efficient crawling and discovery. Although by submitting your sitemap to Google’s Webmaster Tools does not mean that all your pages will be indexed by Google, but it increases chances of Google discovering more of your website’s content and indexing it. By using XML Sitemaps you can tell the search engines about how often you update a page/section of the website and the priority of the pages.

Back in 2007 major search engines (Google, Yahoo, Ask, MSN) agreed to a common protocol for discovering a sitemap from a website using robots.txt. Enabling autodiscovery on your sitemaps makes it easier to manage the addition of new sitemaps across all the search engines.

Sitemap autodiscovery has a very simple line addition to the robots.txt file and is well documented on sitemaps.org.

Sitemap: http://www.example.com/sitemap-host1.xml
Sitemap: http://www.example.com/sitemap-host2.xml