How to transfer music from an Iphone 4 to an Ipod shuffle?

I just got an I pod shuffle for christmas and I was wondering on how to transfer music already in my I phone 4 to my I pod shuffle. I already have a macbook air that I can syncronize the music from my i phone into and then into my i pod. But I don't know how to do it please help!

If you bought the music from itunes-go into itunes on the computer, click on purchased, select what you want to download-then drag the music from the itunes library to the ipod shuffle. If the music was obtained somewhere other than itunes-then the only way to get it off the iphone is with 3rd party ripping software.