We didn't really "prepare for the talk". Mostly it was a series of small talks as situations came up that lent themselves to it.
That's pretty much been our approach as well. Dd12 has a Sept. bd in a locality where you have to turn 5 somewhere btwn 6/15-10/1 to start K depending on the district. She made the cut-off by two weeks by starting in one of the districts with a later cut-off. She then skipped 5th so she is between 1-2.5 years younger than her grade mates (waiting to start kids with bds around hers is common here).
She missed the 5th grade sex ed talk due to the skip. We opted her out of part of the 7th grade curriculum b/c, as a younger 11 y/o, I wasn't too sure on having her learn about anal sex and some of the other stuff they intended to cover including pictures of genetalia with STDs. This was all taught in a co-ed environment by a male teacher she didn't know. They also had a Christian group come in and talk about teen pregnancy which I had an issue with knowing what that often looks like -- which is scare tactics.
I've tried to talk with her ahead of time about whatever I can and, fortunately, she is very open with me so it's been good so far. I'd have to say that now, at 12, she is starting to explore things, like reading the Lovely Bones, that I wish she'd wait on but I don't imagine that I'd be successful in banning her from reading things like that and am still going the route of discussing rather than banning. I read it after her anyway, so it was too late to tell her she couldn't read it.
Being accelerated, she does tend to hang out with other kids in the accelerated/GT classes, who tend to be fairly well behaved kids at least, not the ones who are smoking and experimenting with things I'd rather she avoid. She's expressed a pretty strong desire to avoid that type of stuff as well.
