Hi,
Search engines are really smart these days so basic word substitution no longer really works.
Here are the basic rules around modern-day SEO:
1) Produce great content for a target audience, do it well and be comprehensive.
2) Ensure that your website is optimized for desktop computers as well as tablets and smart phones.
3) Share content on social media and produce content that is so valuable that people link to it from third-party websites.
4) Ensure that your web server is fast and responsive because server speed is actually a ranking factor.
5) Spell everything right. Spelling actually counts in SEO.
6) Be authoritative. Produce amazing content that's the best of its kind on the web.
7) Syndicate your content to third parties like a LinkedIn, Medium.com, all the social sites, as well as Instagram and the emerging social platforms.
There are perhaps five dozen other indicators however if you follow the rules above generally your site will start to rank well. There are technical things you can do to ensure that on page optimization is pristine, however the rule of thumb these days is fulfill of the macro rules and refine with micro rules and you will rank well.