Factors like Meta Title, Meta Description, Meta Keywords, H1 Tag, ALt Text. Make sure that your keyword is included in these fields and also in the URL
Do a proper On-Page audit of your site to see if Sitemap, Robots.txt and other things are in place or not.
See whether your site is HTTP or HTTPS, Page Load TIme are other factors which are important from ON-Page SEO point of view
Do a check on sites like Webpagetest.org and Gtmetrix in order to know where exactly your site is lacking n terms of On Page SEO