Car Alarms: disarm car alarm, valet mode, how to disable a car alarm

Question
how to disable a car alarm

Answer
In order to properly answer this question I would need more information.  You would need to list the exact make and model of the 'car alarm'.

Most car alarms have some type of manual override switch that you would either flip or push with the ignition key in the run position that would disable the system.  This is known as putting the system into valet mode, and would typically disable the security features of the alarm but allow the convenience features to remain operational.