My oldest son will be 18 in November, and he has a girlfriend. She came over the other day, and after we all ate dinner they went in the living room to watch TV. I was in my room, but I left my door open (I want to give him a little space, but there are limits lol). When it was time for her to go home, I came out...and they were making out on the couch. It's not shocking, but it's still a little weird as a parent to see that. I moved off to the side, so it didn't seem like I was spying on them, and loudly called out that it was time for her to go.
Now, my son has known about "the birds and the bees" for a long time; his mother and I have always been open with all the kids about sex so I didn't need to have that talk with him. No, instead I waited until the next day when it was just the two of us and had the real talk.
First, I made sure that he remembered the first rule: you always need to make sure you have consent. I also brought up that he too has the right to say no; just because he's male doesn't mean he has to just sleep or engage with any woman that may ask or pressure him.
Second, I told him that he needed to make sure he always had clean and cut fingernails, and that foreplay is very important. (Yes, sometimes foreplay isn't wanted, but that's advanced stuff, and right now he needs to learn the basics first).
And finally, I told him that even though he may handle himself roughly, it's important to be gentle with her. He brought up that unless she likes it rougher, and I agreed that if your partner says they want your touch harder then you should do what your partner wants. But it's always best to start from a gentle position. You can always go harder, but some people don't like the rough stuff and that starting off that way can ruin an encounter.
I told him that I'm sure it was uncomfortable hearing all that, but I wanted him to have information that my parents were too embarrassed to give, and that if he ever had any questions I would be happy to answer them as best as I could. See, when I was 12 I remember asking my dad a question of a sexual nature, because I was curious. And my father, being mortified and feeling awkward, just lied to me about it (the question was if when the penis got hard it had something to do with sex). I didn't want that lack of trust to happen to me and my son.
Some of you reading that may wonder if you could have those kinds of talks with your kids; if you're not a parent yet, I hope you can. And if you don't think that you could, then you may want to reconsider having kids, because when you do you have to put them first, even if it makes you uncomfortable.