The list of SEO Do's needed to implement, on every successful website

Make sure, you observe these rules when building your web pages (a.k.a. White-Hat SEO):

Take care of web, so the page is quickly loading for visitors (caching, quick servers, local sources).
All images are optimized to lowest possible file size and images are using only required resolutions.
Each image or icon has assigned ALT tags.
On each page is just a single H1 headings.
Remaining headings are ordered in logical way.
Make sure, the site is responsive, thus readable for all devices of visitors.
If possible, try to limit external resources as less as possible, because of loading speed slowdown.
Do not try to cheat engine robots in the code, by serving the visitors different content, as to robots.
Do not use I-Frames because of previous, unless it is realy no other way how to serve the web content.
Make your content interesting and interactive too.
If needed to use a video, store it rather on server itself, then on YouTube - because of longer loading time.
Make the experience of web visit as best as possible. Create clickable links from phone number.
The theme colors should be contrast enough, so text is readable for all visitors.
Place a link to review form of your GMB somewhere, or place it into your email signature.
Use properly Meta-Data for Description, Keywords.
Use Title in Head, so it contains your website name after the title of the article - because of searching.
Create and update sitemap.xml for indexing robots.
Be aware about external links eating Your SEO juice.
Make sure, your web runs on https protocol.
SEF URLs rewritten based on the content. Today is being used dashes and not underscores in URL.
Take care, about content rich site. Visitors needs the reason to return back.
Keep value of code to content ratio balanced.
Place style definitions into page body, in order to decrease resources loading count.
Set properly rules for search engine robots (index, noindex, follow, nofollow).
Use logical and visible navigation throughout the webpage. Eventually breadcrumbs are useful too.
Against the spam, encrypt your e-mails by use of JavaScript.
Implement Google Search Console and Google Analytics, so you can fix issues reported.
Prepare set of Favicons for multiple devices (PC, NB, Tablet, Smart-Phone, Android, iOS, horizontaly).
Also place into the code OG tags, so the page can be shared on social networks effectively.
Make sure to include ReCaptcha v3, if your site contains any form, not to be spammed by bots.

The list of SEO Don'ts needed to avoid, on every successful website

Make sure, you won't use any of the following on your website pages (a.k.a. Black-Hat SEO):

Don't grab an images wherever from internet and then use it because of copyright.
Don't take into consideration the order of headings.
Ignore the optimization for web visitors using different devices. Font size, positions, buttons or links too nearly aside them, will involve visitor.
Do not hotlink any resources found on foreign sites.
Do not try to cheat engine robots in the code, by serving the visitors different content, as to robots.
Don't ignore setup of External links in new tab. Also set them nofollow attribute.
Do not use I-Frames because of previous, unless it is realy no other way how to serve the web content.
Do not use Keyword-Stuffing in assumption, that it will help to get better search result position.
Don't serve the video from YouTube or elsewhere aside of your server, even that you are its author. The reason is slow page, with video loading.
Don't configure the web page background having the same colors as text, even if it contains your KW or target search phrases.
Don't ignore code to content unbalanced ratio.
Do not use Description, Keywords, Title inproper Meta data - on each page should be unique.
Do not write long novels in the Description or Title.
Don't ignore order and length of web page title.
Don't ignore neccessity of sitemap.xml file.
Do not ignore each external link - they eats SEO juice.
Do not take care about website SSL certificates.
Don't use URLs full of attributes, being for engines and visitors quite unreadable.
Don't use in URLs and in filenames underscores.
Avoid the idea, that once the web is built, it is not required to update the content, nor the system.
Don't use external CSS files, as it delays loading of the page. The trend is minify the page these days.
Don't ignore proper setup of rules for search engine robots (index, noindex, follow, nofollow).
Don't ignore the threat of spam flood in your mailboxes, just mailto: e-mail link is not enough.
Do not monitor visitors sources and ignore the hints about errors found by Search Console.
Without monitoring, you will not get an idea, what needs to be fixed on your website.
Do not simply ignore using Favicon for devices.