Descriptive URLs: use a descriptive page url, which should reflect your targeted keyword
Subdomain or subfolder: subdomains are seen as separate domains
Hyphans: split words using hyphans
www or no-www: provide both domains, but set a prefered version in Google Webmaster Tools
Localisation: chookse a country-specific domain, for better local search results
HTTPS: Security is a top priority for Google
URL builder: Use this tool to add custom compaign parameters to your URLs
File extension: do not strip out the file extension on URLs

Meta Information

Title: each page shound have a unique speaking title (60 - 100 characters)
<title>Website Title</title>
Description: each page should have a unique description (max. 160 characters)
<meta name="description" content="">

Keywords

Single: every page shound have a single unique targeted keyword
Research: rank for keywords with high traffic and less competition
URL: keyword should appear in URL name
Title: keyword should appear in page title
Heading: keyword should appear in headings
Content: keyword should apear in ~3% of article length
Meta Tag: you can ommit the <meta name="keywords" content="">, search engines do not use this meta tag

Content: Content matters the most in SEO
Headings: Clear structure H1 - H6 max. 70 characters long
Strong: use strong tag to highlight your targeted keyword
Uniqueness: do not provide duplicated content, use unique content types
Length: article should be at least 300 words
Freshness: new content is important. Updating pages or regulary posting is recommended

File name: use a short descriptive name
Alt tag: add an alt-tag this a description of the image (60 - 70 characters)
Dimentions: add the width="" and height="" attributes to the image
Responsive Images: serve the most optimized image corresponding to the window size
Size: keep the filesize as low as possible
Optimization: Optimize images by removing some meta information

Title: add a descriptive title to links
Backlinks: Only add external links if you got a backlink to your site
nofollow: add rel="nofollow" attribute to external links only to prevent spam and bad links
Internal links: add ~3 internal links to your content

Social Shares: provide sharing options for your site
Social Profiles: add social profiles to your Google search results
OpenGraph: The Open Graph protocol enables any web page to become a rich object in a social graph.
Facebook: Sharing Best Practices for Websites & Mobile Apps
Twitter: with Twitter cards, you can attach photos, videos and media experience to you Tweets
Authorship information
Google+ Authorship: add Google+ authorship information to your page
<link rel="author" href="https://plus.google.com/u/0/[GOOGLE+ ID]"> or
<a href="https://plus.google.com/u/0/[GOOGLE+ ID]" rel=author">Google+ Profile</a> or
<a href="https://plus.google.com/u/0/[GOOGLE+ ID]" rel=me">Google+ Profile</a> or
<a href="https://plus.google.com/u/0/[GOOGLE+ ID]" rel=publisher">Google+ Profile</a>

HTML sitemap: An HTML sitemap allows site visitors to easily navigate a website.
XML sitemap: Help search engines to index your pages
Image sitemap: Increase that your images can be found in Image Search results
Video sitemap: Make sure, search engines know about all the video content on your site
Mobile sitemap: For feature phones, you can create a mobile sitemap

 <meta name="viewport" content="width=device-width, initial-scale=1, maximum-scale=1.0">