Everything Apple (the Mac heads thread)

The way I did it was to ...

1. Quit iTunes
   
2. Move the entire iTunes folder (standard location is in ~/Music/) to the new drive.
   
3. Start iTunes - it should error message that it can't find a library and ask if it should locate one or create one.
   
4. Press locate and show it the new iTunes folder and specifically the .itl file inside.
   
   

This way if the drive is disconnected, iTunes will error when it starts and say it can't find the drive, not resort to a local one again.