most common wiring faults? Got a possible bad earth/live

My car wouldn't start the other day (See thread here) but after a little while the car started to show signs of life.

The problem I have now is that the led for the alarm is going mental and the indicators keep flashing every so often (obviously from when the alarm kicks in)

This to me seems like there is a wiring fault somewhere (maybe a bad earth or dodgy live connection) as I got the car started quite a few times today, but then it's like the alarm just loses power or starts flicking on and off.

Anyone know of the best places to check for wiring faults. I have the dash off and all the wires to dash switches seem ok.

Do I just have to check every live feed and earth till its stops arsing about??

Cheers in advance

Alfie

Is it just the alarm that's going spazzmatic or are there other problems too?

EDIT: A few questions.

What wire was loose to the starter motor?

How does the immobiliser work? Does it cut fuel? Spark? Starter?