While playing one song in iTunes, you can cue up the next by Control+clicking the song or clicking the small three-dots button next to the song name. Select Play Next and the song will start when your current one is over. Once you have done that, selecting another song to Play Next will put the new song first in line. Select Add To Up Next to instead add the new song to the end of the list. Select View, Show Up Next to see and edit the whole list.
Mac Video Tutorials and Tips for Apple Users
