Here's a summary of the best modern SEO rules.
Good SEO is more and more about common sense and having a good site.
Don't use tricks, even if you get away with it today you will be caught eventually
Make good content that serves people's needs.
Use the keywords you are targeting, but don't 'stuff it' full of keywords, you can use varied phrasing of the same topic too. Research LSI (Latent Semantic Indexing)*
Make your site fast. If it's slow, people will bounce, Google will notice and assume it doesn't help users.
Make your site easy to read on mobile too. At least 40% of visits are mobile. Give mobile visitors a great experience.
Meta tags: if you don't want the search engine to choose the snippet it displays in a SERP*, you can provide a suggested snippet in a meta tag, maximum 160 characters, e.g.
<meta type='description' content='Summary of modern SEO rules: avoid tricks, use keywords and variations (i.e. LSI), good titles and meta descriptions; make it fast, mobile-friendly and secure.' />
Title: should be relevant, and unique (please not same title for every page of site, and don't prefix the title with the site name)
You want other people to link to you, particularly 'authorities'. Nurture good relationships with the people behind such sites.
Make sure to use google search console (formerly 'webmaster tools') and google analytics. Look for penalties and warnings.
https. Today, insist on https for any page that has an input or textbox.