I rarely pull out my smartphone in public transport, I usually just wait it out and pay attention to my surroundings. The only time I do is when 1) I'm sitting down in the LRT and, 2) have to set up Moovit to vibrate when I'm near my stop. It then goes back to my bag for the duration of the trip and zippers are sealed with an s-biner.
I think I could only have an album or two worth of songs on the phone. That usually meant looping back to the first song on the list by the time I'm near the end of my nearly two hour commute.
I also preferred to rip my own CDs at 128kbps bit rate and could only afford to store them on a 256MB or 512MB Sony memory stick; hence the limited playlist.
Sleep, listen to the radio. Back in highschool yung driver ng service namin nakikinig lagi sa radio show ni mo twister dati. one of the top songs sa radio during that time was Chasing Cars by Snow Patrol ahhhhh. careless days.
Listening to music on my portable music player of choice (Walkman way back then, and then MP3 player).
Without music? Just staring out the window, or people watching. I sometimes guess where people are up to after they've gotten off. On the train, I sometimes try to guess someone's station.
I sometimes read my school readings, but I tend to have really terrible headaches when I do this, so I just do this when I really have to.