You can stop identity theft from happening to you by making sure you completely destroy any sensitive documents.
Shred documents before recycling or throwing them into the trash or better yet if you can burn the documents.
Never give out personal info over the phone to people you don't know. If someone calls you claiming to be your credit card company or a debt collector hang up and call back to be sure you're talking to the right people and not some scammer.
If it's a true company or debt collector they will understand that you want to call them back to be sure you're talking to the right company and not giving out details to a scammer or other person ready to steal your identity.
Another thing I highly recommend you do and for nobody to be without is get identity theft protection through lifelock.
Paying for identity theft protection will be the best money you'll ever spend. Lifelock will monitor your credit and identity and will alert you to any fraudulent activity and will help you get your identity theft repaired should you need it.