how do i copy my itunes library to an external hard drive?

The following has instructions: iTunes: Back up your iTunes library by copying to an external hard drive

Drag and drop works for me.

Locate itunes folder (in music folder) and just drag to external harddrive.

can take a while if you have a lot of tunes.

I use > Carbon Copy Cloner to backup my entire OS X including Doc's, iPhoto and iTunes.

If you only want a copy of your iTunes Library, go to: Music > iTunes > and drag n drop iTunes Music onto the External HD.