The best way to keep Android safe is to use an antivirus tool; in other words, anything that works to keep malware off your device.
Which Android antivirus app is best? One of the most popular options -- with more than 500,000 installations and a 4.6 (out of 5.0) rating on Google Play -- is AVG Antivirus Free, which also lets you kill tasks that might be slowing your device, track or remotely wipe lost devices, and secure Web browsing against "drive-by" malware attacks. A paid version of the app ($15) adds a number of other features, such as spam call-blocking and an app locker for securing device settings.
Also ranking high on the list of most popular antivirus apps: the free Avast Mobile Security and TrustGo Antivirus and Mobile Security. The latter also includes secure browsing and the Candid Camera Thief ID feature, which begins snapping away after three failed password entry attempts. "We'll email you the photo!" promises TrustGo.
Also worth considering: Symantec's Norton Mobile Security Lite, which includes the ability to send an SMS text to remotely lock a lost or stolen smartphone.