Answer:
The first thing is to learn what the Feingold Program is all about. You can do this by going to the website of the support group, the Feingold Association of the United States: www.feingold.org It explains the Program (elimination of synthetic dyes, synthetic flavorings, preservatives BHA, BHT and TBHQ and Aspartame) and why it is important. There is a good 2 part video on the homepage to get you started.
Read Jane Hersey's Why Can't My Child Behave. You can read Part I on the Association's website.
Go to your cabinets and read the ingredient labels. This will get you started on learning where these additives are. Next I would join the Association so that you have the best information. AThe membership material is invaluable. It includes a Shopping Guide & Foodlist. Volunteers at the Association research brand name foods and publish these books listing thousands of foods of all types (including candies, snacks, fast food, etc) that are free of the worst additives.