Located the music folder under iTunes and connect your phone to your computer. Bring up the explorer and locate the "Music" folder. Select multiple mp4s from the iTunes folder and drag them to the music folder. The phone will automatically bring album artwork and track order correctly to your phone.

The plus side of our phones is that we can take music from anyone with iTunes (or any other mp3's, mp4's etc). We dont' have to "authorize" our device like one would with an iPhone/iPod/iTouch.