=> Sitemap files must use UTF-8 encoding
=> Use W3C Date time encoding for the “last mod” timestamps
=> Sitemaps should be no larger than 10MB (10,485,760 bytes) and can contain a maximum of 50,000 URLs.
=> Submitting directly to them, pinging them, or adding the Sitemap location to your robots.txt file.
=> Use gzip to compress your Sitemaps but no larger than 10MB (10,485,760 bytes)