My daughter has come to me asked the regular questions kids ask about sex, where babies come from, etc.  I have always been very open and honest and told her the truth.  I even got text books and the such so she could learn about human anatomy and what the differences were and why.  She has a very educated knowledge of what sex is and why but it isn't something she feels is dirty, taboo or 'the in thing'.  It is a normal function that adults do in a relationship.  She is cool with that and I think will be a very resposponsible person because she knows and understands the responsibilities of what occurs when you have sex, without precautions and why its good not to have sex until you are actually ready in mind and body.