[Jason] Derülo explained that he did not believe in the possibility of "It Girl" to be the next single from Future History.[7] However, his peers were saying that it was very distinct from the lead single, "Don't Wanna Go Home" and that response motivated him to pick it as the second single.[7] He believed that showing the difference in the new album was important in picking the single. He did not want to put another dance song so that his fans do not assume that the entire album consisted of uptempo songs.
http://en.wikipedia.org/wiki/It_Girl_(song)
Peers, huh? But some critics also rated it well, and according to VH1, Derulo said the fans wanted it as a single. I guess selection depends on how democratic the label is, especially for later singles. For what it's worth, I dislike "It Girl."