I recently upgraded to a new development machine, which means the certificate used to sign my applications during debug changed. Under most circumstances you’ll never notice a difference, but if you’re developing apps using Google’s Maps API you’ll find that your old API key no longer works with the new certificate fingerprint.
Google's instructions walk you through retrieving the MD5 fingerprint of your SDK debug certificate - the certificate that you’re probably signing your apps with before publishing, but it doesn't talk much about the Keytool command.
The thing to remember is that Keytool is part of Java, not the Android SDK, so you'll never find it searching through your Android and Eclipse directories. Mine is located in C:\Program Files\Java\jdk1.7.0_02\bin so you should find yours somewhere similar.
From a command prompt, navigate to this directory and type:
keytool -v -list -keystore "C:/Documents and Settings/<user name>/.android/debug.keystore"
That’s assuming the path to your debug certificate is in the typical location. If this doesn’t work, you can find out where it’s located in Eclipse by clicking Window –> Preferences –> Android –> Build.
There's no need to use the additional commands shown on Google's page. You'll be prompted for a password, just hit enter. The last line shown, Certificate fingerprint, is the key you'll give Google to generate your new Maps API key.