An advertiser wants to improve the position of ads on Google but isn’t willing to raise bids. What else could increase Ad Rank?
Lower bids on keywords with a low clickthrough rate (CTR)
Change keyword match types from exact match to phrase match
Make changes to improve the components of Quality Score
Review impression share data to identify missed opportunities
Explanation: Having better quality components typically makes it easier and cheaper for your ads to enter an auction. Our measures of ad quality also help determine whether your ad is qualified to appear at all.
Read more here: //support.google.com/adwords/answer/1722122?hl=en