For Ginny, it was at the Yule Ball. With Neville Longbottom. She knew Ron would be furious if he found out. So she simply didn't tell him. The only person she ever told about her first kiss was Hermione Granger. Hermione was a little jealous when Ginny told her, since she had never had one. Nevertheless, she still wanted to hear all about it.
"The night was dark," Ginny began poetically. "After trying to dance a couple times, me and Neville went outside. We couldn't dance for long, 'cause Neville kept stepping on my feet. So, anyway, Neville took my hand and told me that he was really happy we went to this dance together. Then.... He confessed that he had a crush on me." Ginny giggled and blushed, "And I didn't know what to say, since I obviously didn't have a crush on him. Everyone knows I liked Harry, then. Although, he was looking more and more handsome in the moonlight. So I just told him that I had a crush on him too. He beamed and then we sat there for a few minutes in the dark. Then the next thing I knew, his face was, like, two inches from mine. I scrunched up my lips and waited. And guess what? Neville turned out to be a really good kisser. Who knew?"