Both times I've had it done I was under general anesthesia (propofol). The first time was rather rushed, and in an emergency room - I actually have a memory of being shocked - it wasn't terrible, but I did form a memory, even though I was under sedation.

The 2nd time (just recently) I also had a TEE (they stuck a probe down my throat to do an ultrasound of my heart) before they shocked me to be sure there weren't any blood clots in my heart (it would not be good to dislodge one!) before they did the procedure. My last memory before the procedure was just counting down while they administered the meds. and then I remember waking up. I think I was out for about 1/2 hour. They did the TEE then shocked me while I was unconscious.

The eletrocardioversion itself is basically the same as the procedure you see in TV shows when they use the paddles to shock someone.

I was able to find a few videos of electrocardioversions by doing a Google search.