SEO

General

• Only use either 2 of H1 tag, URL and page title for keywords, anything more than that will be penalized

On-page SEO

Title Tag

• Use a phrase containing relevant words (say, 8–11 words) with at most 55–65 characters because extremely long phrases will not work well on mobile devices where space is a constraint
• Titles must be precise and concise, and can use a mix of uppercase and lowercase characters
• Avoid commonly used titles or duplicate content because search engines display a preference for unique titles
• Use a simple, unique title rather than a sensational, irrelevant title. Consider user intent rather than looking at titles from a search engine point of view.

Meta Keywords & Description

• The meta description must be unique for each page on a website, like the page title
• Avoid stuffing the description with keywords, and remove all special characters
• Avoid using multiple meta keywords as it can have a negative influence on search engines
• Use meta robots attribute if possible as it is preferable over robots.txt

Heading Tags

• Avoid skipping heading levels on a web page. <h1> should be followed by <h2>, which in turn may have a <h3>, and so on
• Your web page must display a systematic pattern or consistency. If the formatting or styling of the headings is not to your liking, you can use CSS styling to alter it
• Include keywords, but do not repeat them in the heading. Keywords used at the beginning of a heading yield better results. Avoid spamming or using irrelevant words in headings, because doing so may have a negative effect.
• Must have 1 h1 tag for every page, but not more than 1 h1 tag in 1 page

Engaging Content

• Update the content at least every six months, because Google has a penchant for updated or fresh content
• The content should not be irrelevant or stuffed with keywords—the search engines may penalize you for it. However, you can use keywords or close variations of them twice or three times on a page in a logical way. The content should be informative and engage the user, encouraging them to return to check out the site regularly.
• Avoid using a keyword 3 times in 140 characters — that is keyword stuffing. In-depth, detail-oriented, relevant content helps you space out keywords evenly.
• Do not use 2,000 words just to fill the page; low-quality content results in bad UX.
• Bounce rate reflects the number of users who visit a web page and then leave. It doesn't matter how much time they spend on the page; it focuses on whether users leave the site after viewing just one page. Low-quality content results in higher bounce rates and will eventually affect the site's visibility.
• Do not copy content from another website or use boilerplate content. Google search engines have been known to penalize sites that use duplicated content. Focus on user satisfaction and not on fooling the search engines. At times there are legitimate reasons for duplicate content
• Use 301 redirect or canonical tag: <link rel="canonical" href="http://example97653.com"/> to display similar content
• Homepage should have more than 700 words while category page should have 300 words

Image Optimization and Interactive Media

• Use interactive media such as audio, video, images, and infographics to connect with your users
• Use captions and alternate text for media, and build relevant content around these media. You can use a single key phrase in the alt text if it is relevant to that image
• You can interchange images based on the screen size, with heavy-duty images for desktop sites and lightweight images for mobile sites.
• Try to limit the image file size to less than 80–90 KB for optimal page-loading time.
• Use PNG or JPEG image formats wherever possible, because they are robust and have more visual properties. Using thumbnails and different angles for a product can be very handy, especially on e-commerce sites
• Using videos explaining a product or marketing a certain entity is a good practice
• Google owns YouTube, and it can be a game-changing means of branding your product
• Infographics are an excellent way to provide information or create timelines with relevant content.

Outbound and Internal Links

Internal Links

• SEO-related research suggests that no page on your website should be more than three clicks from the home page, meaning all pages should be easily accessible.
• You can use relevant anchor text to point to different pages on your site.
• Breadcrumbs are an efficient way to provide site navigation using links.
• Having a good link structure makes it easy for search engines to crawl your entire website, and easy accessibility also leads to an awesome UX.
• 3 links to your own website

Outbound/External Links

• Sometimes a page includes jargon or topic-specific terms; instead of wasting time explaining supplementary information on the page, you can use URLs or anchor text as outbound links to locations that explain the information in depth.
• Linking specific terms to wiki sites such as Wikipedia and Webopedia may boost your SEO process. Not only is doing so relevant, but it also lends a certain amount of trust and credibility to your site.
• Be sure you do not link to spammy or illegal sites—doing so may negate your SEO efforts, because search engines will penalize your site
• Do not link to sites that are not relevant to the topic, because two-way linking or link farming can be detrimental

On-site SEO

URL Optimization

• Each URL should be human-readable and not consist of a bunch of special characters or numbers mixed with words. It should be meaningful and should reflect what the site is about.
• Using hyphens (-) instead of underscores is a good practice recommended by Google
• SEO experts advocate the use of canonical tags or 301 redirects for duplicate pages or pages with similar content; otherwise the value of the content may be negated, because as ranking signals may split it across the multiple URLs
• For "404 Page not found" errors, you need to use 301 redirects to guide users to a working URL for that content.
• Using a robots.txt file helps inform search engines about pages to be ignored while crawling the site
• You can also indicate broken links and 404 pages in the robots.txt file
• SEO experts advocate the user of a favicon on the title bar next to the URL, because it lends credibility and helps with effective branding

Site Maps

• It is a good practice to include both XML and HTML site maps in your process
• Make sure your XML site maps for search engines are exhaustive; on the other hand, HTML site maps should be more concise so users can navigate them more easily

Domain Trust and Local Domains

• Studies suggest that domains registered for two years or longer were considered more trustworthy than new domains
  Use the .com domain extension, because it is more common than .org and other extensions
• Domain localization—catering to a specific country or city—may prove to be a game changer
• Opt for a simpler, unique, relevant domain name rather than a sensational name, to help users connect with your site
  focus on your prospective customers and come up with something catchy and easy to spell that they can relate to

Mobile Site Optimization and Responsive Websites

• Make sure that the site is responsive
• The bounce rate will be lower for responsive sites, because users can get the same information on mobiles as well as desktops
• Currently, Google marks websites as mobile-friendly in mobile searches to help its users identify which websites are likely to work best on their device.

Site-Loading Speed

• Minify CSS, JavaScript, and other files
• Minimize HTTP requests
• Use an efficient server configuration and good bandwidth
• Archive redundant data in the database, and cleaning out trash and spam
• Use fewer plug-ins and third-party utilities
• Interchange data and images, depending on the screen size
• Avoide inline styles, and keeping presentation separate from markup
• Use a content delivery network (CDN)

Off-page SEO

Social Media

• Users can share and promote your website
• Keep your audience engaged, and share updates with them
• Use the capabilities of these social media sites for branding and advertising for a fraction of the cost of traditional marketing methods such as television advertising, press releases, and Yellow Pages listings

Blogging

• Informative content on blogs acts as supplementary information about your products or services
• Troubleshooting steps, product-relevant content, and meaningful information are some of the elements that can be included on a blog
• Inbound and relevant links from your blog to your site can boost your SEO implementation significantly.

Localization and Citations

• Google My Business allows you to list your business and gain prominence in SERPs
• You can place your products or services and categorize them so that they show up when a search query is used for that category or niche in the region
• Information such as working hours, updates, and contact information can be provided, leading to better accessibility.
• Local SEO utilities such as Yelp and Foursquare are extremely helpful for understanding the pros and cons of your products or services, courtesy of user feedback or input
• Reviews help you establish a connection with users and understand their viewpoint and concerns related to your business
• Increasing interaction with your users will help streamline your business in the long run.

Inbound Links

• Links from domains with high page rank and authority are preferable and lend more credibility than links from domains with low authority or low page rank
• The number of domains that link to your website can be a crucial factor
• Studies suggest that links from several different domains to your site can boost your SEO implementation. However, you should not indulge in link farming or use underhanded techniques, which may result in a penalty
• Referral links from blogs, social media sites, and news aggregators are handy, provided they are relevant and contextual
• Inbound links from another domain's home page or key pages are more useful than links from a sidebar or an insignificant page location.
• Google recommends getting links from domains with high-quality content.
• Backlinks from social bookmarking sites (such as Reddit) and web directories (such as DMOZ) can affect visibility positively.

References:

• Introducing SEO: Your Quick-Start Guide to Effective SEO Practices