Think about the sales professional that described the alarm system to you. He should have been professional during his presentation, knowledgeable about the alarm system, accurate in price quotes and willing to answer all of your questions directly. All of these things are important when choosing and rating systems.
Consider the installation process. In order to give the security system the best rating, the installers should have been professional and courteous while doing a quality installation.
Pay attention to the response time. Every alarm system company recommends that you do a performance test of the equipment periodically. If the response time of the monitoring center and authorities is within the specified time frame, you may be able to give it a high rating.
Rate the ease of use. A good alarm systems should make you feel safe, not frustrated. If you have problems arming or disarming the system, you will be less likely to use it like you should. A top quality home alarm system is user friendly.
Look at the outdoor sensors and monitors. These should all be weather proof and able to withstand the elements. Some fading of colors is normal--other than that, they should look the same as when they were installed.
Determine the cost to worth ratio. You have to decide if the amount you spent on the home alarm system is worth the money. If you feel that you should have gotten a better system for what you paid, that may be a sign that you should consider a lower rating.