Hold power and volume up,,,,after you see M logo count 3 seconds,,,push volume down and it should say android recovery.
Tell me what you get. If you do see android recovery push volume up. That should put you in your custom recovery if you flashed one.
From there you can wipe your system and try again.
If your just getting fastboot protocol, connect to your pc (do you have official cable)? ,,,,,Start adb and type "adb devices" to make sure your recognized, you should get a string of letters and numbers. I am assuming you know where your running commands from. Did you ever enable USB debugging?
Your getting hung up because you have an incomplete install.
Try getting file from somewhere else as well or finding a recovery like ClockworkMod, Solarnz R4C, or Rogue.
Custom recovery goes a really long way.