1.get a techsheet or diagram

2.DMMeter ur suspected wire according to ur techsheet or diagram and mark it however you like (tape, marker...)
-assuming youre familiar w/ the alarm's diagram:

3.mount ur antenna, LED, valet, shocks sensor, antitheft bypass (if needed)

4.know which wire youll need and which you dont need and cut it(short), so you dont have all those wire there to confuse you.

4a.separate all the wires according to its route.

5.use split looms to insulate the wires, cause it easier to access if you happen to need another wire _taken out_ from the bundle or another wires (like antenna, LED, valet, shock sensor) _wrap into_ the bundle. this will save the mess of wires running everywhere under the dash.

6.after all the wires are ran to its place, tap them in(not t-taps) and solder them one-by-one.

NOTE:if you happen to run some wire to the fender area, note that water might get in. for example on the late model, honda civic and acura RSX. caulk it!!

-use a bicycle brake line for ur fishing line through wire walls or door boots. very useful tool.