Ok, let me recommend one thing first...get some sort of data logger so you can get your gauges correct after. You will almost defineatly run into problems. These sorts of things have gotten a bad rap over the years because people mess up their readings. Easily fixed when you have reference. Borrow one from someone.
I did this on my talon when i was younger, i wired mine into a button right next to the dash. Just get a mulitimeter out and find which pin of something close, like your cruise control, sunroof, or whatever, gives you 12 volts when you turn your lights on. Another easy way is if your wiring harness for an aftermarket stereo has an illumination wire (not sure on accords of the top of my head).
