Here are five quick rules for a secure android device:
1. Always protect your android with a Lock Screen, such as the built-in pattern lock (set a secret swype pattern to unlock), a PIN Lock (which uses numbers to secure your hendheld) or a Password Lock (using both numbers and letters).
2. Rooting your device is a security risk and should stay unrooted.
3. Always download applications and games ONLY from the Google’s official market.
4. Use a firewall or a app that offers something similar to a firewall, Droidwall is a good iptables based firewall and easy to manage.
5. Keep your wireless and bluetooth connections turned off, turn it on only when you need it.
And one more thing if your smartphone gets stolen, misplaced, or you lose it somewhere, make sure you have installed a phone locator ( find your phone) application.