I'd reincarnate on Earth, in Canada, in a decently wealthy family, but not a rich one. Also, a decently open minded family, I wouldn't want to be with xenophobic, homophobic, racist, etc people after all.
I'd be your perfectly average girl, though somewhat prettier than I am right now.
... And that's about it, I don't think I'd change anything else. I mean, I'd rather be in a world where I'm familiar with most things and the common sense and stuff, though in a wealthier and safer country than mine. Also, modern technology is a huge amount of comfort, and I doubt I'd wish to change that for pretty much anything.
If I had to make bigger changes, I'd go to a fantasy equivalent of modern Earth, which would basically be the same as our Earth, but with magic. And my magic would be teleportation, because I'd love to save up on travel time.
... And if I was absolutely forced to make even bigger changes, then I'd go with a world that is year-round at a warm temperature and that the concept of clothes didn't exist and that snu snu was something viewed as completely normal and that anyone could do with anyone (with consent, of course). So I'd willingly go into those hentai situations while being naked 24/7 and then go back to my everyday life as soon as I was done with that.
And if I had to make even bigger changes, then I'd tell whoever was in charge of reincarnation to just send me to heaven, because I already did enough! >.<