Where to put an Alarm Module

Where should I but the siren at under the hood I mean?

the best place for a siren are under the air cleaner, under a head light, along the firewall... anywhere there is room where you can drill the holes, shoot the screws, run the wire (tape off the first few inches then loom it to make it indistinguishable from factory engine wires), and most importantly make sure it faces down to the ground.  keeps water out.

as for the brain... some like to put it under a center counsel, but the best place is way up in the dash.  look at the factory wire you are about to use and try to make it look like that when you are done.  get some split loom and black tape and put it back to factory.  you dont have to tape everything, but you dont want a theif to be able to see red and pink wire and trace them right to the brain so they can unplug it.  some cars dont give you much to work with but be creative.  alarms and remote starts are nice to do because they give you a chance to be you, to make that install yours and have nothing else like it.  after doing deck after deck you dont really feel like an installer.  and when you are done with the alarm, you know how cool it is and how you overcame different stuff, but the customer get the little remote and assumes everything was easy and it better work.  they wont know/care if you threw in a relay to do trunk pop, or made the effort to find the tach signal, they assume thats how it should be anyway.

everytime you do an install, you should try and beat your last one.  not time wise, thats dumb.  practice routing and finding wires, different ways to tuck brains and take advantage of extra channels ect.