It All Comes Down to Club Lighting

My basic rule of thumb is that it all comes down to club lighting.

To be a proper DJ you need some form of spinning disco light or
starball (like a mirror disco ball) some form of flashing light (not a strobe, colored is best) and some portable spot lights.

Then, use accordingly. Flashing for fast songs, spinning for slow, with spotlights used as needed to lighten up the area. Black lights are always a good idea.