Well, the answer is simple: nothing at all.
We woke up to hear the news about the terrorist bombings during the Boston marathon, and the many casualties. The work of cowards, who don't like to fight with fair means. What will they reach by this atrocity? Nothing, except that those who learn about it will feel more nationalistic. The goverment will take anti-terrorist measures, and if you are in line at the customs, you'll curse those terrorists who are responsible for your delay. That's human nature. If someone jumps under the train (happens every now and then on the line I travel) the usual comment is: 'Couldn't he/she have chosen another train? Now I'll be too late for work.'
I am of a mind that, when you have a problem with someone or something, you should seek a solution that works for both parties. But you don't do it by blowing away buildings and killing people, you try to talk about in and give and take some.
Turning to terrorist actions is a cowardly action, and shows only your incompetence. Cowards will try to bully you, but if you address them directly and show no fear, they turn away. They can't argue with you, you're the cleverer one. Once, twenty odd years ago, my sister and I were travelling to Zurich by train, and we shared our compartment with an ayatollah imported from Iran to 'convert' some muslims in Germany. He began to talk to us, looking down his nose because we were only 'indecent' western women, but his every arguement was quickly turned around by one of us. In the end, seeing he got nowhere, he just left the compartment and went to another train car.
I am against violence. I see no use in killing innocents, never have and never will. Why must people fight wars? Because of greed? Because of the economy? Certainly not because of religion, although it is used by many as a scapegoat. When you read the Bible, the Koran or whatever, you fill find a message of love and respect. No order to kill others to get better of it. But some extremist give a totally different meaning to some of these writings, to justify the atrocities they commit. And lots of less intelligents follow them, just because they are given a promise that the afterlife will be better than the one they have. Education could do a great deal in getting this out of the way. That's why young girls are killed in Yemen, because they want to attend lessons.
Sorry if I ramble a bit, but I don't like where the world is going. Hopefully the culprits will be punished soon and lasting solutions can be found.