Children have different learning needs and levels of understanding when an adult wishes to teach him or her something important. Different children need different levels of interaction depending on their age, level of maturity, and if they have any comprehension difficulties. If your 3 year old was scheduled for a CT Scan, you would use simple, visual descriptions to help him or her understand what the big machine does and if it will hurt or not. The same protocol is necessary when educating children regarding personal safety.
Personally, I believe the biggest disservice any parent can do for their child is to use and teach the child silly baby names to identify their specific private area. Children who learn to call their genitalia names like Willy or VA jay jay may be confused if asked about their penis or vagina. In addition, children will be less credible should they need to testify regarding sexual exploitation. However, as adults we should educate children that some people use silly names for their private parts.
With younger children, tell them that their private parts are the parts covered by their bathing suit. Explain that except for certain situations such as a parent assisting them with bathroom hygiene no one should touch then in those areas. If someone is asking to touch their private parts they should say no and run and tell a grown-up. In addition, children need to understand they should not be touching anyone in those areas covered by a bathing suit.
My own children would ask me, how I would know if it is a bad touch versus a good touch. I explained that if the touching made them feel icky-yucky in their tummies then it is not an okay touch. Children have to understand that even though a teacher or scout leader may be an adult that if the adult asks them to do something they know or feel is wrong it is okay to question what they are being asked to do. Teaching children to voice concerns when asked to do something that makes them uncomfortable is not a bad thing.
When we were growing up, we were due to the times expected to do as told and not to ask questions. Silence is golden when someone is hurting a child. Make children aware that you will protect them, but in order to protect them, they must tell you if someone scares them or hurts them. Bad people will make all kinds of threats to keep children quiet. I will kill your mother, father, sister, brother or pet. I will kill you. I will make sure your mother or father never locates you.
Assure children your job as a parent is to protect them from the bogeyman if they tell you when someone makes them feel unsafe. Teach them who three safe adults are that they can talk to if you are not available. Some people think that educating our children is instilling fear into them, that is not true. Children need to practice what they would do in all situations, including practicing fire drills and safely getting out of the home. As a parent we teach our children how to respond to an emergency, that is our job here on earth. Teaching includes the good, the bad and the ugly.