To improve your quality index, focus on making your ads as compelling as possible (while keeping the ad very relevant to the keyword and landing page), so that users will be more likely to click on them, thereby possibly increasing click-through rate.

Here are some tips to help improve your click-through rate:

• Create different versions of your ads and use ad testing to help you determine which ads perform best. Try testing different copy strategies, different offers or different display URLs to see what works best.
• Look at the ads of your competitors. Are your ads as compelling? Is your offer as strong as it could be? Consider including a special offer in your ad to encourage users to click.
• Make sure that all of the keywords in your ad group are highly relevant to the ads and geographic settings for which they are displayed. For example, if one or more keywords in your ad group are not performing well, consider moving those keywords into another ad group and writing ads that are highly relevant to those keywords.
• For best results, be sure to include your keyword in the title and description of your ad. Use the Insert Keyword feature to help you do that automatically.