Don't give them any ideas.
The idea of giving ideas is a complicated one. We need to think about how we can be attacked, so we can spend limited dollars protecting against the most likely attacks, but also to prepare people for other attacks we won't stop (so they won't let it bother them so much), and to figure out how to work around the resulting damage.
But in discussing the possibilities, we also give people ideas.
For example, during the sniper attacks in DC, I really thought the constant coverage would give terrorists the idea to replicate this on a nationwide scale. I can tell you our area was effected far beyond reason during those three weeks, with real economic and "freedom" effects. If there had been 20 terrorists carrying out that attack, and if they had worked to NOT get caught instead of working to get credit, we could easily have seen hundreds, if not thousands of dead people.
And when California was burning a couple of years ago, because it was so dry, it occured to me that a terrorist could load up a car with molotov coctails, and simply drive down the highway in the middle of the night throwing them every five miles or so. A simply attack, but possibly devastating.
And of course now we know that a single well-placed car bomb could have destroyed much of New Orleans -- and if it was done in clear weather in the middle of the night, thousands would have died in the flood waters.