I developed my first Android app a few years back and at the time it was using Admob for mobile banner ads. Google bought AdMob a while back, and the time has come where Legacy AdMob usage is being retired this month (August 2014) and so you need to upgrade to the Google Play Services based Google Mobile Ads SDK.
First. Wow. I have to say, the steps and docs for how to do this seem to be spread over many different places. I’m not sure if all of these places actually walk you through the same steps just written in a different way, but it’s taken me a while to work out what I actually need to do. Some useful refs:
If you logon on the AdMob site, it will prompt you to complete a data migration step and update some account info – take care of that first here.
Steps for moving to the Google Play Services based advertising seems to be covered here. I’m currently working through these steps for one of my apps, if I come across anything useful to share then I’ll post another update later.