SEO can be split up into two separate categories; On-Page
SEO & Off-Page SEO.
On-Page SEO refers to all the things that you can do ON your website to help you rank higher, such as page titles, internal linking, meta tags & descriptions, etc.
Off-Page SEO refers to all the things that you can do directly OFF your website to help you rank higher, such as social networking, article submission, forum & blog marketing, etc.
1. Page Titles
2. Meta Descriptions
3. Meta Tags
4. URL Structure
5. Body Tags (H1, H2, H3, H4, etc.)
6. Keyword Density
7. Image SEO
8. Internal Linking