So PolicyMic did a great article about 17 Lies We Need to Stop Teaching Girls About Sex. I definitely agree with these, but there are a few more I'd like to add:
1) There's a definitive sex act. - Sex isn't just a handful of activities. There is a mind-boggling, near-infinite amount of ways to have sex. And, I promise, if you think you know all the ways to do it, you don't. Not even close.
2) You shouldn't have to talk about sex. - If you want to have a good sex life, you're going to have to get used to talking about sex. Before sex. During sex. After sex. With new partners and life-long partners. It's a discussion you'll be having for the rest of your life. Learn the language early.
3) Orgasms are the goal of sex. - Not everybody comes every time. And that's okay. So long as everyone's having a good time, orgasms aren't the be-all and end-all. They aren't a sign of success anymore than not having one is a sign of failure. Pleasure is pleasure; trying to chase one kind is just going to make you miss and dismiss all the other kinds.
4) Only people who can't find people who want to have sex with them masturbate. - Masturbation isn't a consolation prize; it's maintenance. You'll never know--much less be able to let anyone else know--how your bits work, if you don't pop the hood yourself on a regular basis. Whether or not you're having sex with someone else.
5) Sex is something you're instinctively good at - You won't be good at this first crack out of the box. Like ever other skill in the world, sex takes time, practice, and knowledge to get right. And every partner you'll ever be with will be different. Find the joy in learning how to please your partners.
6) It's the other guy's job to be good at sex. - Want awesome sex? Don't rely on someone else to give it to you; give it to yourself. Speak up. Your partner isn't psychic; they're not going to know what works and what doesn't unless you tell them.
7) Real sex looks like porn sex. - Real sex feels amazing. But, out of context, it looks freaking ridiculous. Stop worrying so much about what you look like and sound like. You're never going to get to your orgasm, if you're too busy worrying about what your "O" face looks like.
8) Sex isn't important. - It is. Even if it isn't important to you, chances are good it'll be important to your partner. If you aren't sexually compatible with your partner, it is a big deal. Dismissing it as unimportant doesn't make it so. And will cause far more problems than it solves.
9) Sex is leverage to make your partner do what you want them to. - It isn't a bargaining chip. Your partner isn't a puppy in training and your sexy bits aren't a dog treat. Granting or denying sex to manipulate your partner's behavior is messed up and mean. And reflects pretty poorly on both of you.
10) Sex can fix anything. - Sex is awesome. It feels great and builds intimacy. It's healthy and fun. But it doesn't fix anything. Sex--even great sex--doesn't make problems go away. It doesn't make people love you more. It doesn't make you love them more. It doesn't forgive or forget. Sex can feel pretty miraculous at times; that doesn't make it a miracle-worker.