How do you hook up four twelve inch subs?

That depends on a great many things;

- are the speakers 8, 4 or 2 ohm

- are they single or dual voice coil

- what is their RMS power handling

- How big an amp(RMS), or how many amps are going to be used

- what load are those amps stable at - can they be driven down to a half or a quarter ohm

- etc, etc.

I have put this question on my watchlist, so feel free to add more info so I can give you more/better help.