What are the most 3 important factors to improve the quality score of a keyword?

Include specific keywords that directly relate to your specific theme.
It's often more effective to use keywords that are two or three words long instead of just single words.
Using the Google's Keyword Tool to help you think of additional keywords.
Regularly review your campaign performance.

1.
Content Related Keywords 2.
Try to add keywords in the Heading 3.
Keywords in the description 4.
Make two or more Ads to check the performance.

1. Click Through Rate (this is the most important factor)
2. Ad Copy relevance
3. Landing Page Quality

 

keyword relevance i.e landing page content quality keywords in ads, title or description relevant ad and ad group