According my experience to increase quality score you need to make sure that
- The keywords you are targeting in the text ad is in your page title and the content
- Try to add keyword in Header line and description.
- Use related keywords exists in your website
The above points will increase QA score.
1) Landing page with keywords similar to your ad
2) Keywords matching your ad and description
3) Long tail keywords
4) Narrow down by city
5) time of the day , choose the right time when clicks can be cheaper