How to recover from a bad flash? I've killed my phone. I tried to install CyanogenMod following a tutorial, but now my phone won't start. How can I recover it? Is there a tool can I can use to reflash it?
Probably you werent running the specific firmware on which the CM port for your phone was designed to be installed on. Check if you had missed any steps in the tutorial.

If your phone gets stuck at the bootlogo or bootanimation, you can try to do a factory reset from the recovery mode. If the problem still persists, try flashing the stock firmware and then installing CM.

If your phone does not respond at all while attempting to switch it on, its hard-bricked. The only way to recover it is by using jtag. You need to disassemble the phone for this method, so it's better to take it to a service centre. Here the bootloader is rewritten to the device using a riff box. Watch this video to see how it's done: https://www.youtube.com/watch?v=B_zaehAFjME