Settings => Tap something seven times to make USB debugging visible
Settings => System (developer options) => USB Debugging
Android Studio
DL Android Studio, Java SDK, and "latest USB driver"
The Android tutorial made it sound like I needed the Asus driver for my Asus Nexus, but the Asus driver threw a "no device driver found" when I tried to install it to the Nexus device under "Other" in DM. However, the "latest USB driver" from Google, ostensibly generic, worked.