There are many varieties of low carb diets out there. Atkins, Paleo, South Beach, and the Primal Blueprint are just a few. The one thing they have in common is a focus on lowering carb intake.
The first step to successfully following one of these diets is to nix the processed foods. There are a lot of low-carb processed foods on the market, but it's best to avoid these, too. Focus on natural vegetables and fruits in addition to meats for you diet. All refined sugars and flours should be avoided.