What should we do to fight against terrorism?

We are going through a really tough condition. We just experienced a nightmare in Mumbai attack and still we cant belive it that it happened. But the matter of fact is it happened and it is not only happening in a peaceful country like India, but it is happending everywhere. The major concern is that why it is happening and what can we do to prevent such happening. We have to share our thoughts regarding this as we have to be united and fight together for this. What do you have to say?