Are you getting all of the bids? You may be to cheap.
Are you losing all of the bids? You maybe specing the wrong equipment, or your bid is to high.
Are you about 75%? Then I would say you are just right?
Go for the most up front, and then let them "bargain" you down.
I bid the highest that I can get away with without losing the job, and then towards the end of the install, if they have been well behaved clients then sometimes I provide a "gift". Each install would dictate that gift. Perhaps they could use an extra camera, or there is some electronics thing unrelated to the CCTV install that you can "tweak, repair, or tidy up the wiring ect".
Getting people to call you is the hard part, getting them to except you bid is the easy part.
You need more CCTV info?
http://scorpiontheater.com/cctvmag.aspx