Optimized URL Structures
User-friendly Navigation (breadcrumbs, user sitemaps)
Optimized Internal Links
Text Formatting (use of bold, italics, etc)
Properly optimized H1 tag and other headings
Image Optimization (image size, proper image names, use of ALT text)
User-friendly 404 pages
Fast-loading pages
High-quality Fresh Content (This is the most important On-Page SEO factor!)
External Links (No Broken Links or Links to 'bad' Sites)