If you're going to go out and run for over an hour, you might want to carry a little extra fuel.

I don't know how much is enough, or too much. I'm still learning. I can say with confidence that it's best to eat something before you start to feel faint : ) I also have found that the goo or gel type of fuel seems to work best for me, for fuel on the fly during races. I prefer bars for hiking or longer slower runs. I wasn't able to find my favorite flavor (Clif Shot Mango) last time I looked at a local store, so it occured to me to try online. The best deal I found, somewhat to my surprise, was on amazon.com... $15.22 for a case of 24, and eligible for their free shipping. So I bought a book, too. Damn their marketing gimmicks, and my susceptibility to them!