Okay... did i do things wrong?

previous morning, i wake up 6 am (which i have experimented 4 days to found my excellent REM lucid dream phase) and doing WILD technique. At first, im doin well and everything go smoothly using the visualizing "I am dreaming" words behind my eyelids and suddenly, it seems like i entered lucid dream. when i tried things out, everything suddenly go pitch black and im feeling mad vibration, then i woke up(not FA or anything).

my question, did i do things wrong?
what happen?
is the scene before the mad vibration just a active imagination?
when im lucid, what are the first thing i must do?

From the sound of it (and from how you described it in the DV chat), you did go into a lucid dream, but then you woke up into sleep paralysis.

Yes, like ShockWave said. The first lucids people have usually ends very quickly. Next time try to relax and just look around you. Activate your sense of sight and feeling first of all, you can do this by focusing on your hands and rubbing them together. If the dream is stable after that, then go have fun! :)

Could have been a false awakening, very comon.