Two of my favorite quotes:

"The cost of freedom is always high, but Americans have always paid it. And one path we shall never choose, and that is the path of surrender, or submission."
- John Fitzgerald Kennedy

"He is most free from danger, who, even when safe, is on his guard."
- Publilius Syrus

For the next several years we have to learn how to live with these threats. Living in Fear is exactly what the terrorist want. We need to maintain our vigilance and go on with our daily lives.
Remember to report any suspicious activity to your local police or the FBI.
The new information that has recently been released is that you should keep 3-5 days worth of extra supplies in your home in the event of a terrorist attack.

Go to the following site. Read it, VERY IMPORTANT AND INFORMATIVE :
http://www.ready.gov/index.html

FOX News also has an excellent informative page that answers a lot of your questions in a way you can understand:
http://www.foxnews.com/story/0,2933,76887,00.html