To do list to grow SEO from coding perspective?

Are there any to do list I should add to my code? I use PHP. No framework. I don't think to use wordpress as I have monetization strategy in mind later, and I prefer to do with code later.
For example,

1. use <title> and meta:desc
2. Use <h1> once in every pag
3. don't forget to add the code from google search console

Anything I miss?