Keeping your address book up to date is always a tasking process. While a few apps exist that supposedly comb your contacts for updates, those only work if they actually update their information. Tech blog Digital Inspiration has come up with a simple Google Script that you send to contacts so they can update their information themselves.
The idea here is that instead of contacting each of your contacts and manually updating each one, you send out a webform they fill out and that information is automatically added to your Google Contacts. The process requires you to make a few changes to a Google Script to add your own information. After that all you have to do is click on who you want to send it to and it's done. You contacts will receive a very simple form to fill out and that information gets plugged into your Google Contacts. If all your contacts actually reply, you'll have an up-to-date address book. Head over to Digital Inspiration for the guide and the Google Script you'll need to use.
Keep your Google Contacts Up to Date! [Digital Inspiration]