This would mean you must be prepared for the following: 1) Active Shooters, 2) Explosions, 3) Chemical threats (water supply), 4) Biological threats, 5) Cyber attacks, 6) Radiological Dispersion Device and even 7) Nuclear threats, especially with the deal the US has just made with Iran. But sophisticated weapons are not required. Something as simple as a can of gasoline can be prove to be a deadly weapon.
The links above can offer some suggested preparations for a terrorist attack, but I would suggest that the BEST preparations are being armed and staying out of Gun Free"Sitting Duck" zones where almost all mass public shootings occur. Otherwise, learning to say Allahu Akbar is an alternative that might save your life.
What is a Terrorist? The definitions are broad especially if you look at the legal (FBI) version. In most cases, they are evil people who hurt innocent people, but not always. George Washington would have been considered a terrorist by most any of today's standards.
Often times what the government might call terrorists, the other side calls Freedom Fighters. Suppose a US President were to stage some type of crisis at election time and "temporarily" suspend elections, effectively taking over as a dictator. Anyone who rose up in armed resistance would be classified as terrorist. This said, anyone who beheads or burns people alive because their religion is different is purely evil. Still we must be careful to not judge all people of that religion based on the radicals or crazies.
For more information:
Graphic Video of Paris Terrorist Shootings
Blog Table of Contents
The Best Gun
Natural & Man Made Disaster Preparations