My child does things that are hygienically troubling to those around—spitting, picking their nose, licking fingers, putting a hand in their pants.

These often have a reason of the child's own—self-soothing, checking, itch or discomfort—and they tend not to decrease with head-on scolding. First observe when they appear; if it's from boredom, anxiety, or sensory needs, prepare an alternative—another hands-on activity or a chew item. It also helps to teach the specific place/time where it's okay ("touching your body is for a private place"). If skin or nose discomfort, or strong repetition, is present, also check for a physical cause at a medical clinic.