What criteria is being used by search engines to rank websites?

While no one outside of Google knows for sure what criteria is being used to improve organic search rankings, it is widely believed the most important factors are:

• Good, relevant content. Develop content for your website that will satisfy a problem customers
  are looking to solve.
• Websites that are being updated frequently with good viable content. It is important to update the content on your website regularly. Google places a higher value on online properties that are trying to stay current with search inquiries.
• Links from outside sources that are linking to pages and content on your website. It is also helpful to create internal and outbound links to relevant content.
• Websites optimized for mobile devices. Consider adding a security certificate (https) to your domain. Some SEO experts believe Google is valuing websites with a security certificate a higher organic ranking than those without a security certificate. For more information on improving search rankings view the following resources.

AMA: Search Engine Marketing: http://bit.ly/2ePiYIl