What to say, when to say it??

I've been getting a lot of questions lately from my daughters. Questions that are tough to answer. Sometimes I feel a little unprepared.

As a child I don't remember anyone having the "talk" with me. I want my daughters to feel like they can ask me anything, but how do you know what is age appropriate and what is not?

How do you make sure you child is not holding speaking engagements on the bus, providing missing details to all the kids who's parents aren't having these types of "talks"?

It has always been my philosophy to answer honestly but to not provide a lot of additional information unless there is another question. I'm proud to say that my oldest understands the mechanics (I think). However, I have my suspicions that she is trying to convince her younger sister that what I've told her is true. My suspicions stem from overhearing this.

Middle daughter harshly whispering to oldest daughter, "If you don't want to tell me where babies come from, then don't, but stop making things up."