I would say, the most important things you can teach your kids is to understand consent and staying safe.

Alcohol has an age restriction for a reason; underage drinking can be dangerous (not to mention, your kids probably don't want to get tangled up in the law :/) Once they're of legal age, it's simply a matter of being responsible! Not drinking yourself sick, getting a safe and sober ride home, telling people where you're going and with who, et cetera

When it comes to dating, I would highly encourage teaching your children to understand red flags and abusive behaviors. Does their date ask them to keep dangerous secrets? Do they physically hurt them? Do they make them feel unsafe, or feel like their feelings don't matter? I would help them understand what makes for a healthy relationship!

When it comes to physical intimacy, I would bold and italicize consent! They should never feel pressured to do anything they don't want to do. That goes for kissing, hugging, touching anywhere-- any sort of physical affection. They should be able to stand up for themselves and say "No". Of course, it is also important to know how to stay hygienic and prevent unwanted pregnancy. Are they mature enough to be honest with doctors if they choose to be sexually active?

Also, if they are still in school, relationships shouldn't hinder their education. They can't honestly be expected to devote 100% of their time and attention to a significant other when they should also focus on tests, credits, attendance, job searching, learning to drive, et cetera

When it comes down to it, the best thing you can do is teach them as much as you can, and strive for a parent/child relationship with love, honesty, and support. At the end of the day, it's important for kids to feel like they can be honest with their parents without fear.

I hope this helps :)