[Hawk]

you have 2 methods. One is the mic clicker. Click once to start or stop a song. Twice to advance to the next song and 3 times to go back (if the song has played more than a few seconds, it will go back to the beginning of that song. you have to triple click again to go to the song before that one.)
The other method is to double click the home button. Your iPod controls should appear onscreen without unlocking. If they don't, you need to go into settings and activate this feature.