Quality Score is very important in Google Adword PPC campaigns because on this basis you'll be charged by the Google, this is a number which is assign by the Google 0 to 10 for each keyword with respect to the landing page. There are many things which makes the quality score, if we have good quality score about 8 or 9 then we charged very less. If we are bidding $3 for a keywords then we'll be charged about $1 or $1.5. Here we have some point which shows the factors on which quality score depend.
1. Ad copy - should have a keyword and call to action 2. Landing Page content and Quality - should be relevant to the ad on which visitor will click 3. Landing Page loading time 4. Ad quality with respect to all keywords 3. Use a specific page ( Destination page) rather than home page.