Keep it clean: Always put the little rubber dust cap back on. It keeps grit from clogging the internal channel.
Don't over-tighten: They are hollow, which makes them fragile. Snug is enough; you aren't trying to fuse it to the metal.
Gravity vs. Pressure: In cars, you usually need a buddy to pump the pedal while you crack the screw, though vacuum bleeders are a great "solo" alternative.
Brake Calipers/Wheel Cylinders: This is the most common spot. If your brake pedal feels like stepping on a marshmallow, there’s likely air that needs to be purged through the bleeder screw.
Clutch Slave Cylinders: Similar to brakes, manual transmissions use these to keep the shifting crisp.
Home Radiators: If your heater is cold at the top but hot at the bottom, a bleeder screw (or valve) lets out the air pocket blocking the hot water.
Cooling Systems: Many modern cars have bleeder screws on the engine block or thermostat housing to prevent airlocks after a coolant flush.