Yahoo - just go ahead and forget about them, the rest of the internet has.
Bing and Google are the two big players in the US and most of the world, but you did mention Yandex. They serve a particular market. So the question becomes, WHERE is your target audience? If it's the USA, then you don't need to worry about anything other than Google and Bing (maybe DuckDuckGo).
Google has the strictest guidelines to follow, so as long as you adhere to their guidelines, usually you'll have no issues with Bing. Bing does let you get away with more things and formats things different (JSON-LD, for example, was only recently approved by Bing - prior to that you had to use a different markup).
The only TIP that I can give you when it comes to SEO is to build the site as you would like to read it as a user. Don't try to trick the search engines, they're too smart. The text on the website should be in easy to read human format. Forget about stuffing keywords into a sentence, they will come naturally.
There's a whole slew of info that you can find online, but please pay attention to the dates of the articles that you read. Reading things from 3 years ago sometimes are way out of date and the rules have changed. That said, I have articles from 2001 which are still valid today!
Do the research, then cross check and find a "current" article to make sure the information is still valid.
MOZ, Search Engine Journal, and Search Engine Roundtable are great places to read articles - although they can get a little in-depth if you're not ready for it.
Many SEO Companies (including ours) write blogs on a regular basis and have them on their websites, so have a hunt around and read articles there.
Finally, Google is your friend. If you have a specific question, Google has an answer. You will not get a great answer if you type in "how do I do SEO", much like you wouldn't get a great answer for "how do I build a plane". Be specific in what you're needing, and you'll get tons of answers.