Bully
50 Achievements
Watch Your Step
Trip 25 people with marbles.
How to unlock the Watch Your Step achievement in Bully - Definitive Guide
Marbles are a prank item used to trip people over. They can be found throughout the game at specific locations, as well as purchased from the Comic Book Store. The first place in which you can find them is behind the school bus near the homeless man in the school grounds. Once you reach Chapter 2 you can purchase them for $3.00 at the Dragon’s Wing Comic store in town. You can hold a maximum of five bags of marbles at one time.
Once you have marbles you will need to equip them by navigating through your weapons with or . Once you have them equipped you can either throw them directly at someone by holding and then pressing . Alternatively you can just drop them on the ground with and wait for people to walk over them and fall over. The latter method can be a lot quicker as you can hit multiple people with one bag of marbles. An effective method is to put lots of marbles in the hallways of the boys dormitory and then pull the fire alarm which is located on the wall outside your bedroom. Everyone will start running around and will start to fall over your marbles. Once you have hit 25 people with marbles the trophy will unlock.
You can track your progress for this trophy in the Stats menu by pressing and then navigating to Stats > General > Pranks > People Tripped With Marbles. The below video shows where you can can buy marbles from as well as the two methods described above on how to use them to trip people.
More details in the video: https://youtu.be/cTraFPf39WE?t=1m25s (watch from 1:25)