My first time was when I was a Sophomore in highschool. My girlfriend at the time was a freshman, and a bit of a bigger girl, but very curvy. We had touched and rubbed and licked and played with each other several times before we actually had sex, but mostly it was teasing, we were rarely alone long enough to get anything out of it.
We were at a friends house just chilling when their dog got loose and started running away. Our friend went to chase it down, so we were alone for, god, less than a minute, but we saw the opportunity and took it. Nothing planned, so I didnt have a condom or anything, she just laid down at the edge of our friend's mom's bed and I went right inside her, no time for foreplay. I pulled out a minute later when it sounded like our friend was back, but there was no way I was going to last that much longer anyways.
Ended up doing it for real in her living room about a week later. Her dad and sister were home, but they had to leave to go out of town and pick up her mom from something, so about an hour there and back. They left and I "left", then went right back in about 2 seconds later. This time we had planned it out. She was freshly shaved (my favorite) and got completely naked right there in the living room. She sat me down and sucked me off, cleaned me off with her panties, and started sucking again to get the condom on. All told, I lasted barely a couple of minutes, but just kept going. Was surprisingly good, considering how bad we were both at it, and how anxious I was about not just ruining it.