Children are full of questions, and they will seek answers where they can. Being an "askable" parent is the best way to ensure that you will be your children’s primary source of information and values. Tell your children you want to answer their questions. Never punish, tease or judge them for asking a question, and don't try to avoid sensitive or embarrassing topics. If you don’t have an answer when a question is asked, say you need time to think about it and then get back to them. And, to encourage your children to continue to ask you questions, respond by saying, "I'm glad you asked!"
Source: The Parent Institute