What are the main and most important factors to improve your page rank on search engines?

I fully agree with Mr Ali. I believe the keyword in the title tag that grabs the audience attention , and keyword length which should not be too long so that he audience do not loose patience are most important. 

Keyword in Title TagTitle Tag Starts with Keyword

Keyword in Description Tag Keyword Appears in H1 Tag

Keyword is Most Frequently Used Phrase in Documen

Content Length

Keyword Density

Latent Semantic Indexing Keywords in Content (LSI)

LSI Keywords in Title and Description Tags

 Page Loading Speed via HTML

Duplicate Content

Image Optimization

Recency of Content Updates

Historical Updates Page Updates

Keyword in H2, H3 Tags

Keyword Word Order

Grammar and Spelling

Helpful Supplementary Content

Multimedia Contents

Number of Internal Links Pointing to Page

Quality of Internal Links Pointing to Page

There are many factors that affect Page Rank but keep in mind that in order to be successful in SERP (Search Engine Ranking Position) you need to have advanced knowledge of technical SEO. Also know this the algorithm changes several times a week so planning your strategy on a handful of factors can be disastrous in the long run, with less competitive markets you might get away with it but most of the time you will definitely not. There are many common factors such as the meta tags, keywords, content, linkbacks  but there are other factors such as the load speed, open graph markup, structured data mark up, visitor traffic signals, CTR, domain relevance, length of domain etc. This is just to name a few of the factors.

If you are asking about Bayt search engine then the answer is 'keywords or proper keywords'. If you are asking about any page, then SEO.