I'll never forget the first time I ever went down on a girl.
I'd been flirting via AIM with this young girl I met off of a singles website. One Saturday night, she called me and asked if I wanted to come over. I'd worked that whole day (at the time, I was working a job where I had Wednesdays and Sundays off) and was planning on just staying home that night. However, I dug this girl and wanted to meet her, so I decided to go.
We started making out on her couch shortly after I got there. I reached down between her legs and could already feel how wet she was (of course, she wasn't wearing any panties). After not sucking on her tits hard enough for her tastes, she took one of my nipples into her mouth and sucked it raw to demonstrate how she wanted me to suck her tits (and all her other body parts too, apparently). After a little more foreplay, we adjourned to her bedroom.
I knew from the many porno movies I'd watched that I needed to find her clit and work on that to really get her off. Well, I found it and started sucking it with a vengeance. I alternated between licking inside her, fingering her pussy and sucking her clit. I just kept licking and sucking as much as I could. Her moaning and screaming REALLY turned me on, so I started licking and sucking on her clit even harder. She started moaning and screaming out my name. Louder and louder she got, pushing my head down on her pussy so she could feel my tongue deep inside her. I just kept licking and sucking away, losing all track of time while I rocked that pussy with my tongue and lips.
After several minutes of this, she stopped.
I would repeat exactly what I did above 6 or 7 more times that night, bringing her to orgasm twice, according to her.
I now know FOR CERTAIN when a girl has had an orgasm.