You shouldn't have it until you are in with someone you really care about, you need to be prepaired and know all the risks invovled. Pregnancy and STDs are abound so considering condoms (GOOD ONES THAT AREN'T EXPIRED) is important. 12 is waaaaaaay too young, people have it at all different ages, but doing it before your ready is a bad idea. Most people have horrid memories of their first time because they were pressured into it.
If you make sure it's with someone special and knows at least the basics, it'll be better. Also- lube, use lots.It helps.