Plug your miniSD card into your card reader and navigate to the card's /boot partition. This is the smaller of the two partitions.
If you have a GNU/Linux host machine, you can simulate enabling the Serial Getty Service on what will be the Raspberry Pi's serial console.
Plug your modified miniSD card into your Pi.
Plug in your power cable.
Plug in your USB cable into your Raspberry Pi and your PC.
Open a serial terminal program such as minicom.
Change your serial device in the program to match your OTG registered Pi.
Press Enter 2 or 3 times and wait a few seconds.
This last step is probably the one you are missing.
Connect monitor and keyboard and apply power to the Raspberry Pi.
Sep 07 19:41:20 raspberrypi systemd: Started Getty on ttyGS0.
Hopefully this debugging and setup guide helps.
Try /dev/ttyACM0. My laptop is running Ubuntu, and, when plugging RPi 0 W, nothing fancy happened, but I managed to listen to it by that port: ACM0.
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