How do you talk to children about sex?

This is very sensitive and important issue to discuss with kids accordingly to their nature of mentality and age.
My daughter is near about 3 years old. She have right now sense about her private parts of body. I acknowledged her time to time, that she have to change her clothes in separate room and be aware about your surroundings. You should always pamper or cover your feminine parts from all strangers too. Accordingly to age always guide to their kids about sex and their body. Take care always about their self.