Here are a few things you can try on the command line :
- lsusb
- Does this show your device? If not, something is wrong with the driver - or your device is not connected (broken cable?).
- adb devices
- Does this show your device as attached? If not, a problem may arise:
- the phone is not configured for debugging mode (described above, you must first enable the developer on the device).
- /etc/udev/rules.d/51-android.rules, linux/osx, , ...