There are white markings on trees to show that you're on the AT. If i remember correctly, yellow blazes (markings) constitute a side trail off the main trail.
We hung our food very diligently. The local animals are very familiar with this situation and I'm sure come around very often from foolhardy people leaving food unattended. Also, at the shelters you can hang your food above you which helps stop the porcupines which go after food as well as shoes. From having done a good amount of time in the backcountry, i'd definitely hang my food. I've had to deal with hungry deer, moose and black bear. You should also hang things such as toothpaste, feminine products, deodorant, etc. If you are a light sleeper, you'll find out relatively quickly all the noises around you in the forest. I started using earplugs years ago so i wouldn't wake up at every sound.
If you have more questions, ask away. Also feel free to ask me on my page.