Increasing your ad rank by improving quality scores and using automated bidding (or at the very least enhanced CPC). Google gives each ad vying to win an auction a literal rank to decide who’s ad to show, so in order to increase your impression share you need to raise your rank. Make sure your ads match your landing pages as closely as possible and that you are letting google’s algorithm decide when to bid and how much to bid as soon as you have enough conversion data. Budget is a major lever for ad rank but so are the other things I mentioned.