Low-carb diets are effective because most people don't pay attention to what they eat. When we start following a low-carb diet plan, we're likely to consume more whole foods that contain fewer additives and are less processed. These foods are often naturally lower in calories and healthier to boot.
It may be helpful to track foods using a tracking app. There are many free food trackers out there, so play around with your options until you find one you like. You may also prefer to track your carbs on paper (but it helps to have internet access to look up the nutrition information of foods).
The low-carb diet is flexible, meaning you can have any food you want, but keep in mind that high sugar and high starch foods will "eat" up your carb count for the day. Foods like cookies, cakes, bread, rice, and pasta are particularly high in carbohydrates. Any foods high in sugar, like sweetened cereal, pastries, and candy, are also high in carbs.
Fruits contain natural sugars and, thus, carbs. Sweet potatoes and corn are two vegetables high in carbohydrates, as are potatoes. Other foods containing high sugars and carbs include salad dressing, jams, jellies, crackers, flavor syrups, granola bars, condiments, sauces, and many frozen and "boxed" foods.
Just because a food is high in carbohydrates doesn't mean it's necessarily unhealthy or bad for you, but if you're following a low-carb diet, you will need to be aware of the carbohydrates in most common foods. If you're watching your carbs, you should avoid high carbohydrate foods or look for lower-carb foods you can swap out.