Enable USB Debugging Mode on Android Devices

USB debugging is intended for development purposes only. It can be used to copy data between the computer and the device, install applications on the device without notification, and read log data. Enabling USB debugging is different for each Android version.

Android 2.3 - 2.3.7 (Gingerbread)
1. Open Settings > Applications > Development
2. Check the "USB debugging" option

Android 4.0 - 4.1.2 (Ice Cream Sandwich/Jelly Bean)
1. Open Settings > Developer Options
2. Check the "USB debugging" option

Android 4.2 - 4.4 (Jelly Bean/KitKat)
1. Open Settings > About Phone
2. Tap on "Build Number" several times till the message shows "You are now a developer!".
3. Return to the main Settings menu and now you'll be able to see "Developer Options".
4. Tap on Developer options and mark the "USB debugging" option.