Foods to avoid:
Foods high in saturated and trans fat
White potato, bread, rice etc.
Be careful of fat free items, they're generally loaded with sugar
Full fat dairy (low fat has more protein which is a bonus)
High sugar foods
Why are you on a strict diet? Without knowing this the question can't really be answered. Strict in what way? Because you have an illness? Trying to lose weight? Allergies? By the way, as to the above post, there's nothing wrong with saturated fat depending on the source -- some of the healthiest foods are high in saturated fat, such as salmon or other fatty fish or nuts or seeds. The quality of the fat is more important than the amount.
Stay away from processed foods. Fast food restaurants, sugar,salt breads and things like that. The weight will come off faster. Sugar slows down the metabolism, salt bloats like hell and there are alot of very unhealthy things in processes foods that you would not believe are in there. Example,antifreeze, human hair and sawdust contributing to mental health issues and being overweight.
When you are on strict (weight loss?) diet you need to take care to get enough vitamins and minerals.
Common high-calorie foods include: potatoes, rice, pasta, pastries, cookies, meat, fish, eggs, chocolate and other sweets, nuts, seeds, raisins, cheese, oils, butter, margarine, jams. Fruit juices and soft drinks contain lot of calories.
Low calorie foods: most vegetables, except potatoes, beans, peas, lentils, berries, oranges and many other fruits, mineral water...