In between page content, levels or stages
If your app is a game with different levels or stages, consider placing an interstitial ad in between one or more of these stages. A break between levels provides a natural stopping point for the user and allows them to properly evaluate an interstitial ad. If your app is not a game but has many pages or sections, then consider placing an interstitial ad after a number of screens or actions taken. Avoid placing an interstitial ad every single time that the user completes an action.
Click to view an example
It is recommended that interstitial ads appear before the break page rather than after it. Break pages often require a user to tap a Next button (or equivalent). Ads between levels and after a Next button can be surprising. It is strongly recommended that interstitial ads between levels or stages show explicitly before any Continue or Next level buttons. This behaviour may reduce accidental ad clicks from users who unintentionally click the ad instead of the Next button.
If an app encourages frequent and/or repeated tapping by users, then it is recommended that a delay is inserted after the end of a level and before the display of an interstitial ad. This delay could take the form of a loading or please wait screen, or a progress bar/wheel. This offers users a chance to stop tapping the screen and consider carefully what appears next, and may help to reduce accidental clicks. Click to view an example
Account for potential ad latency
Operator network latency can potentially affect delivery of interstitial ads in your mobile app. This latency may cause the ad to appear on the user's screen at inopportune or unintended times. Consider what the user may be doing in the time window in which the interstitial ad is expected to appear, and consider pre-loading your interstitial ads to reduce latency when displaying them to your users. For more information about pre-loading your interstitial ads refer to the AdMob Interstitial Ad developer guidelines for apps developed for Androidand iOS.