probably the first kiss for alot of people is in kindergarten through 3rd grade. (mine was kindergarden) but the first kiss that has meaning behind it is right around when everybodies hormones kick in, about 13-16
I had mine at 12, that's probably too young. But as long as you love that person, then it's fine. But word of advice, the first girl I ever kissed, I liked her more than I've ever liked anyone ever. I would give anything for her. But 2 weeks after I kissed her, she got a boyfriend. I was heartbroken. So make sure he or she likes you back the same way you like them.