MY FUCKING EYEBALLS ARE ON FIRE!!! That is why I tend to walk to the back of the room. Whether you are in a club with lights already, or you bring in your own, please do not blind people. The main point of focus is center stage, so if the line of sight for someone 5 to 6 feet tall, anywhere on the dance floor, is blinding, you are ruining the vibe. The same goes for lights that are just generally too bright or overwhelming for the mood, even if not in your eyes. If it is done right, and artistically, then it can work, but if you are in a dark forest at night, but the dance floor looks like it is day light, you are doing way too much. If your party is in a tiny space with only 50 people, there is no need for 30 moving lights.
The same also goes for blinding the DJ or performer. They need to see what they are doing and be able to see the crowd. You want to either have the lights facing down onto the top of people's heads, or from the side. I'm no lighting expert, but you want your lights to enhance the event, not hinder it.
Lots of people are kind of reserved when it comes to dancing, so if you see the dance floor in front of the stage is dead, but hundreds are crowding around just outside of where the lights hit, then you should dim those fucking things. People scatter like roaches when they are not trying to be under the spotlight and are trippin.
Lights can set the tone for what you are trying to accomplish with your party. If you want it a bit more social and upbeat event, the lights can be a bit brighter. That way people can see each other and talk. If you want your party to be more of an underground feel where it's all about the music and losing yourself, keep it darker in there. Everyone has their preference. I personally like it dark because I don't like to socialize when I'm on the dance floor. I may not be dancing, but if my head is bobbing, then I'm really into the music and want to zone out.
It is always good to have a second room, even if there is no music in it. One dark, and one bright. If your main room is dark, your side room that is bright can be where people talk. If you want your main room a bit brighter, your dark room can be a chill space with pillows and shit.