Don't remain running in the background unnecessarily
OneNote for Android currently forces itself to stay running in the background using on average 22MB of RAM. That isn't very much but if the app doesn't need to be running all the time it would be better if it didn't. Looks like it is because it leaves a Service called ONMSyncNotificationRemovalService running all the time. Perhaps it is just a simple case of a developer forgetting to call stopSelf or stopService when it has completed its task that requires it to remain running in the background.
The Android SDK documentation calls leaving a service (app) running unnecessarily "one of the worst memory management mistakes an app can make".