So I went out yesterday, I was a friend and a few friends of his. One of whom I was talking to all night long, I really enjoyed the conversations we were having and I could tell that she did too.
At some point, we decided to head back to my friend's dorm and continue drinking there. The girl and I went to the balcony and kept on talking, at several instances we would also stare at each other (in hindsight, maybe that's when I should've been more assertive and gotten more physical) while talking, and with small smile.
Due to a drunk dude heckling us, we went back inside to the common room and joined up with the rest. As I was getting myself another drink, one of my friend's other friends showed up (he has a lot of friends).
Immediately he starts talking to her super-closely, like almost being all up in her face, after a while they go to a corner together and stay there for the rest of the night.
At that point I had given up and continued having fun with the others, and finally went off to bed.

Now my question is, how do I become like that? This dude showed and literally met her for the first time, and ended up sleeping with her. From the way they were talking it was obvious that he was making very straight-forward remarks, as she was laughing a lot.
I just feel like - no, I know that if I had played my cards better then that could've easily been me.

I guess my lesson learned is that I should be more assertive and not afraid to get physical, especially if I'm already having a good time.
What would you guys suggest?