How much research I have to do depends on the nature of the story. For fantasy, none at all.
It is always hard when reality intrudes on belief.
Don't try to write to the trend of the moment.
In loquaciousness lay insanity.
Living gives you a better understanding of life. I would hope that my characters have become deeper and more rounded personalities. Wider travels have given me considerably greater insight into how cultural differences affect not only people, but politics and art.
Getting inside the mind of a terrorist wasn't difficult at all. Even as children, human beings fabricate elaborate revenge fantasies. We're not a particular species. Check out popular video games.