Step 2: Touch the live heater wires together.

Pro-Tip:
Always remember to unplug before touching ANYTHING!
It was the very last thing I had to do to complete the installation of an E3D V6 hot-end. I had done some testing with the hot-end wires simply twisted and taped. The hot-end worked very well.
So after retrieving the connectors I wanted to use for the wireing, I then began to cut and trim the wires. Which is also the exact moment my brain turned on and said *****<many bad words here>*****.
The machine is on, and the hot-end was still on too. But the LCD wasn't on. Anymore.
Sure enough, dead board.
Oops.