According to my experience, best SEO technique is On-page SEO. On page SEO cover 70% work of SEO, in this part, we can do many activities:
1. Website Analysis
2. Content Optimization
3. Website Coding Structure Analysis
4. Technical Error check
5. Website URL, Alt Tag, Meta Tag and Title Tag Optimization
6. Google Sitemap, Robots.txt, canonical errors
7. Website Submit in Google Search Consol, Google Analytics