Search: Google's Guesswork
4. How much you'll be charged when your ads are clicked. The quality score of your keywords works directly to raise or lower your cost per click (CPC). High quality scores save you money on every click, while low quality scores cost you on every click.
In other words, quality score is important. If you don't earn good or great quality scores, your ads will appear less frequently and in lower positions on the search engine results page, and you will pay more for every resulting click.
Improving Your Quality Scores
Because quality score is a quantified prediction for success, the best way to raise it is to do things that are likely to make the keyword successful. There are a huge number of things you can do, the most important being narrowly focusing the keywords you choose to bid on, tightly aligning ad copy to both keywords and search queries, and making sure to avoid the "penalties" that Google can assess when you violate policies or best practices.
You should only bid on keywords where you can write a text ad and deliver an offer that is compelling to the majority of people who would search on that keyword. There are more than 100,000 search queries that could reasonably be matched to the broad match keyword "notebook computer," for example. This huge funnel of search intent makes it very difficult to write ad copy that most of those searchers will find relevant. Therefore, it's hard to get good clickthrough rates for this type of keyword.
You must break keywords down into small ad groups so the text ad copy is directly responsive and relevant to every different search query the included keywords may attract. Don't be afraid to split large ad groups into two or more smaller ones to enable a better match between keywords and text ads.