When you're passing your BlackBerry Pearl on to someone else, or for whatever other reason it's time to wipe it clean of all your accumulated e-mail and applications and other personal stuff, the process is remarkably simple.
Step1
Go to Settings-->Options, Security Options-->General Settings and then click the trackball (or on the 8110 Pearl click the menu button) and select Wipe Handheld
There is then a comforting series of confirmations that prompt you to verify that yes, in fact, you really want to strip everything off. It's pretty unlikely you're going to wipe the device by accident. Do note that wiping it cancels any service you have set-up (ie Blackberry Individual Solution or Blackberry Enterprise Solution). The actual process of clearing it takes a few minutes and you'll be cautioned not to remove the battery until it's complete.