There are many ways to lock a BlackBerry;—so you don't make any unintended calls, for instance

The nifty black pouch that ships with many BlackBerry models can conveniently aid you in locking your device. That is if you're using it to regularly holster your smartphone. But, you need to tell it that's what you want it to do.

Here's how:

From the home screen, press the BlackBerry Menu button-->Options-->Security Options-->General Settings-->Lock Handheld on Holstering. Here you can specify that you want the device to lock when you slip it into the sleeve.

You can also determine whether you want to allow yourself to make outgoing calls while it's locked. You can always answer an incoming call when the phone is locked, but if you're someone who makes calls on the fly -- or in a panic -- you may want to enable outgoing calls so you're not fumbling to unlock when you need to dial.

To unlock, you will be prompted to press the * and Phone keys.