By frequently resetting your lock combination, you decrease the chance that someone will break into your luggage.
If someone watches you open your luggage at baggage claim while going through security or at a hotel, they may break into your luggage when they encounter you on another leg of your journey.
Change your lock after every major flight or trip to help keep your items safe.
Avoid easy to guess passwords, as well, such as sequential numbers, all the same number or birthdays.

Open your lock by inputting the current combination.
New Prestolocks have a factory set combination of "0-0-0."
Turn the shackle 180 degrees.
Press the shackle down and turn it 90 degrees to the left or right.
Input the new combination.
Move the shackle 90 degrees so that it is 180 degrees from its locked position.
Take your hand off the shackle and pull it out.
Turn it back to the locked position.

Push the shackle into the lock and turn at least one of the lock's dials.
Write down your new combination.
Keep this paper in a safe place for future reference.