Let me tell you, I have messed up a lot in raising my kids. I've made some monumental mistakes with them over the years. Things I swore I'd never do. Things that make me cringe when I think about them. It's truly the grace of God that my children aren't more screwed up than they are.
Sex is like fire. When kept under control, it is an amazing, beautiful, valuable gift from God; when allowed to roam out of its appropriate boundaries, it can cause life-altering destruction. With this in mind, and with much humility on my part, I'd like to point out the most common things I see friends do when discussing sex with their kids that I fear will backfire on them in the long run.
1) Don't wait too long. I understand the desire to keep your child innocent and protected from the unhealthy sex-saturated culture around them. But the unfortunate fact is that, as long as you live in that culture (and there's no escaping it completely), the culture will have some say. You will simply have to broach the subject before you want to. There's no way around it.
If your children reach the point that they realize there is this wonderful, mysterious thing out there called SEX that everyone else seems to know about and talk about and giggle about, and their parents don't want them to know anything about it . . . you've already lost a battle. You may not have the honor of being their first source of information on the topic, but you want to be able to quickly follow up on the first -- and you darn well want to be sure you're their primary source of information on the topic, because almost every other source they will stumble upon will be dreadfully misinformed and will not have your child's best interests at heart.
2) Have more than one "talk". This goes hand-in-hand with number one. Your child will hear about sex and need some questions answered long before they are ready for the full anatomy and physiology lesson. Stop thinking about this in terms of THE Sex Talk. There are many sex talks. Feel free to give information in dribbles, on an as-needed basis, over the course of many years.
As your kids get older, look for opportunities to increase their knowledge at a healthy pace. TV and movies tend to open that door. Remember: if a particular bit of information is mentioned or hinted at in a show that you know your child's peers are watching, then you should assume that your child's peers know about this and your child is likely to hear about it soon. Better that they hear about it accurately from you. In addition, talking about sex in frequent small bits will make taking about sex easier, which leads me to number three . . .
3) RELAX. I realize for some of you, this is easier said than done, but I'm telling you -- you have to work on this. Your kids will sense your discomfort, it will make them uncomfortable, and they won't come to you with questions -- and you want them to come to you with questions. This is NOT a topic you want to leave to the schools and the world.
Yes, sex is a big deal, but that doesn't mean you have to make every sex discussion a big deal. A quick word in the car on the way home from school in immediate response to a remark from your child will probably be much more effective than stealing away into a private room when you get home to sit face-to-face, hand-in-hand, prepared for profound and deep revelations. Talking about sex casually does not necessarily encourage an inappropriately casual attitude about sex. I promise you, their friends talk about it quite casually and talk about it ALL THE TIME (and homeschooled parents, don't think your kids are any different). Your reticence doesn't give the subject a sense of holiness; it merely gives you the appearance of being repressed and out of touch and, again, an unreliable source of information. Be accurate, be honest, be sincere . . . but try your best not to be too intense.
So, there you go. Offered with much humility and with no guarantees -- I mean, every kid's different and I'm no expert. But now my mind is eased a bit. Thanks for listening. :)