speaker wiring, with amp and head unit

i am putting in a 4-channel amp into my system to run all 4 of the door speakers, each on a separate channel.  it is an aftermarket alpine 9827 head unit.  i have a couple of questions that I can't find the answers to anywhere.

1.  how do you connect the speaker wires into the entire system?'

2. do you disconnect the speaker wires from the head unit? if so how? do you just cut them or do you unhook them?

3.  what do you do with the wires you disconnect if you have to disconnect them? just leave them there or do you run those to the amplifier?

any help at all would be greatly appreciated!!!

The deck becomes a preamp when you connect an external amplifier.  The speakers are powered directly from the  amp, and the Alpine head unit acts as the preamp source.  It will not provide power to the speakers and will not be connected directly to the speakers.  It connects to the amp via RCA cables.

Run new speaker wires to all speaker locations from the amp.  Tape the ends of any unused OEM wires so they don't touch to ground.  Don't cut any wires off the head unit, just tape off the ends so that there is no bare metal showing.

Next time, just start your own topic, and include more information (equipment, vehicle, etc.) in your question so we can better help you.  As it stands, we don't know anything about your setup- are you adding a 2 channel or 4 channel, what head unit do you have, how many preouts does it have, etc. 

If your head unit has preouts for front and rear, use those.  If it does not, then you can use splitters.  If your sub amp has preouts, and it's connected to either front or rear preouts on the deck (not sub out), you can use those.  If your deck only has one set of preouts, you can split the signal, but will have no fader controls.  You can use line out converters or use another deck.  There are several ways to set up your equipment, but without knowing what you're using, we can't tell you the best way.