Search Engine Optimization is nothing but make a site visible in the search engine. To rank a site on 1st page of SERP, follow ON page and OFF page activities.
ON Page:
Meta tags,
URL Structure,
H1 tag,
Image Alt tag,
Anchor text optimization,
Schema tags,
Footer optimization.
Content Optimization,
Image Optimization,
Page Speed,
Interlinking

OFF Page:
Social Bookmarkings,
Guest Post,
Blog commenting,
Image Sharing,
Quora Answer