If I had to choose just one SEO tip that has worked since I started, it would be to write content to answer a specific question, not to rank for a keyword, this sounds obvious, but most people do it the other way around: they choose a keyword with high search volume, write anything and everything, and wonder why they're not ranking, people aren't searching for a word, they're looking for an answer to a problem, if your content answers that question better than anyone else, the rest will follow.
The trick is understanding the search intent behind the phrase, google is very good at detecting whether or not your page satisfies the user, you can have the best backlink profile in the world, but if people arrive and leave quickly because your article doesn't answer their question, your ranking will drop, on the other hand, a page that answers a question well, even if it's for a low volume keyword, usually ranks well because the algorithm rewards it with positive user signals.
This principle has worked since google's inception and will likely continue to work as long as search engines exist, algorithms change, tricks become obsolete, but the human need for clear and useful answers will never disappear, if you build your content around that need, you'll always have an advantage, it's the tip that never fails and the one most people ignore because they want quick results.
