If the short term goal is to create terror then the best way to fight it is to go about your life. Think of it this way, take a look at how people die, terrorism is pretty low on the list. If you are going to be scared of AQ, I humbly suggest you don't go near a road for the rest of your life as you are thousands times more likely to die driving.

(The per capita death rate for all Americans, of any age, in 2003 was 14.9 per 100,000, or 14900 per 100 million in motor vehicles), 30% of all fatalities of Police Officers in the last century where in traffic accidents.

If the long term goal of the terror is to make political change then you see what it would require for that to come true and the cost analysis of letting them having it or completely destroying any chance of them getting it through terrorism. Make the cost of their method too expensive and they will have to give up or run out of steam.