Parents are actually the most influential factors in teens' decisions about sex, ... It's something a lot of parents don't know. Once they do know that, they feel really empowered. Teens want to hear from their parents about sex and they need to.
It keeps the conversation going, ... You may learn something that you didn't know before. The parent doesn't always have to be the person at dinner table who knows everything. It's OK to allow the teenager to enlighten you about how things really are. They may, in fact, know more than their parents about the way things are in their life.
Don't say 'wait until you're in love,' ... but 'wait until you're this particular age,' or 'until you have been dating the person for a certain amount of time' or 'are in love and can talk openly about birth control, STD's and how sex will change the relationship.' .
I always tell parents: Look at the media that your teenagers are consuming, ... Watch their TV shows. Watch the movies they're watching; read the books and magazines they're reading. That will give you an idea of the kinds of conversations they're having elsewhere.