Wiring 4 ohm subs to amp

How do you know if you are running a sub at 2 or 4 ohms???  Is it the way they are wired together and then wired to the amp?  Speak slowly to me on this, don't use big tech words.

I have 2-12" subs that I want to wire to a 4 channel amp.  I am going to  bridge channel 1&2   and    3&4.  I am putting a sub on 1&2, and the other on 3&4. 

Wiring two subs together and then bridging them is what  you would say is 2ohm.  Wiring the subs individually to seperate channels on the amp is running them at 4ohm. 

I currently have 2-12" subs Audiopipe (TS-PR12YW) hooked up to a 4-Ch DHD NTX-2004.

Those are 4-ohm subs, so you will be running each bridged output at 4 ohms.  I've never heard of those subs or that amp, by the way.  That DHD NTX-2004 amp looks pretty, err, inexpensive, so don't expect it to last too long.

wiring two subs together is called either parralell or series depending on how you do it. this is what determines how many ohms the subs present. bridging an amp is combining 2 channels into 1 output. this determines how many watts will be delivered to the subs. most amps when bridged can handle a 4 ohm load. your subs are dual voice coil and can be wired to either 2 ohms or 8 ohms. with what you have, i would recommend wiring each sub to 8 ohms, then hooking it up to a bridged output. my ultimate suggestion though is to get a different amp.

I am replacing my amp with a Punch 601s or the new P5002.  Using the punch amp, you would still recommend the same hook up with each sub at 8 ohms and bridging them?