my diet mostly consists of fruit, vegetables, pulses and grains that dont contain gluten. i already have unusual eating habits, so it wasnt that difficult for me to stop gluten, and i dont eat any cheese or dairy anyway, so casein wasn't a concern.
gluten is in grains like wheat, rye, oats, barley. so obviously most types of bread, a lot of breakfast cereal, processed food and suchlike. the hardest thing for me to give up was beer, i still indulge in beer occasionally, but it affects me for days afterwards...
i suppose if your used to eating a lot of bread and processed food it probably be a bit more difficult. you can buy gluten free types of bread and stuff, but its pretty expensive, and i dont know if its really any good or not.