AllHipHop.com has an interview with Yung Joc:

AllHipHop.com: So the hook actually turned out to be the last thing, right?

Yung Joc: Exactly, and that�s why I tell people, there�s no protocol in making a record. It could go either way, you could�ve written a hit song before ever hearing the track, you never know. I had to go home and sleep on �It�s Goin� Down� for two days, then I came back and dropped the hook. Matter of fact, we were getting ready for some big party and I�m at the studio trying to come up with a hook or something to make the song right. It was just me and Miss B [of So So Def fame], Diddy, and Chino Dolla were in the studio Everyone left to go get some outfits for the party, except me and Miss B. When they left I made up the hook and I got her to record me, so by the time they got back the song was finished.

Via badboy_uk at BadBoyForever.com.