If you work in a service industry, like, say, a restaurant, do not bring your child to work in lieu of childcare.
If you cannot avoid bringing your child to work for some inexplicable reason, ensure said child has plenty to keep her entertained and QUIET.
If you do not, ensure that she does not make herself at home at a customer's table when said customer walks in, hot and tired and overhungry and CRANKY.
If she does, ensure that she does not say, "Excuse me, that's my seat" when the customer returns from the bathroom, so the customer stands at her own table waiting for explanation from her husband and wondering who
If she does, when the customer asks her son what he wants for lunch, ensure that she does not answer as though the customer is providing her food.
If she does, ensure that
If she does all of the above, do not TELL the customer how cute the child is and ask if she is being a bother. ASSUME she is being a bother, and take her away from the table immediately.
If the customer finally succeeds in communicating to you that the child is a bit of a bother and the customer and her family would like to eat in peace, restrain the child and avoid allowing her to run past the customer's table multiple times, whispering and teasing the customer's child.
If she does, make sure when the customer takes her son to the potty, your child does NOT scold the customer for bringing the boy into "her bathroom".
These tips should help you avoid having customers want to return with a tranquilizer gun and deal with the problem themselves.