When my child can't buy something they want at a store, they lie down on the floor and cry. With people watching, how should I handle it?

In the moment, put safety before explanations or promises, and move to a spot away from the shelves and the flow of people. Say briefly, "You wanted that. We're not buying it today," and save any further persuading for after they've calmed down. As prevention, you can try showing what you'll buy in a photo before heading out, giving your child one role, or keeping the trip short. If they hurt themselves or others, or if a state where going out is nearly impossible continues, share the specific situations with a local support office or a specialist.