Title tag,
Meta Description tag

Forum Posting, Blog Posting, Bookmarking this are the off pages activities.

Professional SEO solution experts have key knowledge about On-page and also have potential to enhance website traffic & ranking. On-page SEO consists of : Webpage content, URL structure, Keywords, Analyze website using webmaster and Google analytics, Proper Schema, User Friendly and Interactive website layout, Redirect issue such as 301, canonical and 404 and Internal linking.

There is no best. You have to do mostly all by keeping the following things in your mind:
- Quality Content.
- High Quality and Relevant Backlinks.
- Promotion.

key word density is one of the most important on page seo and also img alt tags are important.

Title Tag Optimization
Meta tags
Alt text & Hyperlink optimization
Header Tag Optimization
XML Sitemap
Keyword Density Management