Wear safety glasses when cable connected the 3D printer and the laser head is plugged (not only when the laser actually works).
There should be always command M0 used after home command (G28) in G-Code, to give user opportunity to prepare material on bed and connect laser head.
3D printer’s bed should be covered during laser work, to protect it from damage.
Laser head should be disconnected soon after finishing the work.
Never use reset button when laser is connected (unplug it first).
Remember that working area is 86 mm shorter in Y axis when laser is used.