The Google SEO algorithms of today use much of the same criteria as they have in the past. Just as before, your site should have a great navigational structure, SEO-friendly text with a good keyword density, valid HTML code, proper meta tags, credible links to your website, etc.
However, with the changes in the Google SEO algorithms, your SEO-friendly copy now needs to be updated regularly with accurate and unique content that is helpful to the visitor.
Moreover, your SEO-friendly copy needs to be connected throughout your site. Google SEO algorithms now look at a set of pages and compare their content to deem how relevant your website really is. This is called latent semantic indexing and it's a spammer’s enemy. The other criteria changed by Google SEO algorithm updates are links, inbound and reciprocal. Links now need to be created over a span of time. They also need to be varied in their link type: the number of reciprocal links needs to be comparative to the number of inbound links.
Moreover, link anchor text should also be varied; using the same keywords when creating reciprocal links will trigger Google SEO penalties. This is a lesson the real estate market learned the hard way.
Finally, your site needs to be a part of a community, proving your site has "word-of-mouth" credibility. This requires off-page optimization. You need to create a buzz about your website, using forums, blogs, press releases, social media outlets, and more. This tells Google SEO algorithms you're valid and popular and ultimately will be beneficial to searchers.
If you've practiced ethical Google SEO methods and have a website that provides a real service to your visitors, you should be excited about these Google SEO algorithm changes. Google SEO algorithm updates mean your ethical intentions will be rewarded by removing the cheaters, those using unethical Google SEO methods to rank higher than you.
If you've practiced unethical Google SEO methods, such as link building schemes and keyword stuffing, Google SEO algorithm updates are bad news for you.