Only set your interstitial ad units to your app. When somebody clicks, you will get high CPC. The other process to increase CPC is to set which Ads you want to show or not. First thing is, you have to download all the Admob Ads’ list by CPC rate as a PDF file from internet.
For More Information Please Refer: https://www.quora.com/How-should-I-increase-my-AdMob-CPC-and-eCPM