10- Have the dance floor be somewhat symetrical, made of wood, certainly not concrete.
9- Put twice as many amplifiers as you think you need, they will not distort as much. Then put in a few more as spares. Do the same with your speakers. You will hear a massive improvement in the sound. Place all amps very close to the speakers to minimize the wire run and signal loss. Buy oxygen-free line cable and run all the lines balanced when possible. Get silver braided speaker cable or equivalent.(very pricey)
8- Invest in proper acoustic treatment and soundproofing for the room you play music in so it doesn't sound like an airplane hangar. Define a stereo soundstage in the room where there is a left (LEFT) and right (RIGHT) side rather than having the sound installer convince you that it'll sound better by crossing everything up as an 'X'.
7- Have a professional test the room with various impulse signals, pink noise and the rest to establish which speakers may need time delay to generate a coherent image that arrives to your ear at (approximately) the same time. Buy, install and set the above time delay units if needed.
6- Make sure the sound system has enough headroom that when playing at maximum level the mixer's output is NEVER in the red. There should be anothe 10db of headroom in reserve. Playing a system near maximum insures getting distortion.
5- Remember that the weakest link in your signal chain will immediately degrade the sound, i.e.: some cheap processor inserted in the loop of your mixer will insure that the sound stays crappy even if you did all the above. A cheap mixer will insure you stay within the mediocre range most clubs seem to find 'great'.
4- Have you ever listened to a proper external phono pre-amp ($25 or so, used) rather than using those average ones in a usual DJ mixer? This will do wonders for your sound when properly tuned to the type of cartridge you use.
3- Use JBL 'bullet' tweeter arrays, not piezo-electric ones, which sound like....crap. Those will add a sense of realism to your highs when clustered and delayed properly. (see #7)
2- Add proper amount of sub-bass speakers in the room. Most clubs never have HEARD bass yet. (they think they have) Go to Stereo in Montreal, or Vinyl in NYC. Listen to the bass. Draw your own conclusions.
1- Don't let club owners cry they have no money for the sound. They always find money for the bar. There is a possibility that if your club's sound is THAT GOOD it will eventually become a legend. Which club do you remember that became a legend because of their bar???
The real Top 10 would be for an audiophile dancing and listening environment. None currently exist on this planet today, except maybe in some private or corporate home theaters and listening rooms. Check out some live concert rigs run by real professionals. The really good ones can put any club sound to total, utter and complete shame.