I think that:
1. One should be aware of things that don't seem right (i.e. luggage, packages etc. that are abandoned).
2. People acting suspiciously or bizarrely should be noticed.
3. We should get at the roots of terrorism: Ignored people....their hunger, health and education...and do something about it.
Together with those things, Tailsgirl is right on the money. WG is correct about finding and correcting fanaticism. Fanaticism generally happens when those seeds are cast on fertile ground....much like Messianic beliefs occur in oppressed populaces.
The seed has to take root and flourish and it must be nurtured by those who profit by it. They are the ones must be convinced that this is not "the way to go" by education...gentle or harsh. Unfortunately (because it's so simple), nothing is gained by violence in any of it's forms. The Mahatma was so very correct in this thinking.
There are, however, some exceptions to this: Overwhelming Evil (i.e. Hitler) could never have been responded to with nonviolence.
This is a very complex issue and the definitions of what is "political" resistance and where it ends and where "terrorism" begins are not simple.
In general, I find that "Doing unto others...", trying to be gentle, caring and loving work. There are, however situations that demand active and lethal defence.
The idea, I believe is to act in time to prevent the necessity for "letahal action", to make life good for all
G-d's creatures but not to forget you are entitled to the same.