The most important grains to eliminate are wheat, barley, and rye. Some people also cut out
fruit. If you cut out
fruit, as well as grains and added sugar, it makes for an extremely low-carb diet, but to me, cutting out fruit is going a little too far.
Look into the paleo diet. Some people on paleo eat fruit, and some don't, but there is no paleo diet that includes processed foods, added sugar, or grains.