When you bring home a rotary cutter, look at the safety guard. It is there for a reason and that is to protect you and the people around you. There are two positions for the safety guard. It slides down to expose the blade in the "open" position. Slide the guard up and the blade is protected and can't cut, which describes the closed position. Never leave the blade "open" and unattended.
Always close the guard when you are finished with a cut. Notice I didn't say when you are done cutting fabric for the day. I meant each time you finish one cut. Otherwise, an exposed blade could cut skin, fingers, bare feet and toes. And not just your skin, any precious child’s skin in your sewing area is at risk.
I warn students in my quilting classes about open blades, but they sometimes forget. Once I've had a student cut someone, but more times I have seen students cut themselves. I've seen students wave an exposed blade around. In this instance, they are usually “talking” with their hands while holding a cutter. It’s dangerous, so don’t do it.
Always wear shoes when you are cutting fabric. I know a friend of a friend who cut a tendon in her foot after dropping a rotary cutter accidentally. Make sure your family members wear shoes if they are in the sewing room.
Never use a rotary cutter when you are tired. If you are not a morning person or you have been sewing past your bedtime, then postpone cutting until a time when you are fresh. This advice is for all quilters, new and experienced ones alike.