The first step is to center every meal and every snack around protein. Make sure you buy plenty of high protein foods and learn how to cook these foods.

Any properly-raised lean meat is good, especially lean cuts of beef such as sirloin and flank steak as well as poultry. Any kind of fish or seafood is excellent.

If you are a vegetarian, eggs are spectacular, as well as fermented dairy such as low fat cottage cheese or plain low fat greek yogurt. Whey protein supplements are also an excellent source of protein.

Vegan proteins could include soybeans and tofu, lentils, textured vegetable protein, or plant protein supplements (soy, pea, rice, hemp, etc).

Any plant foods that are high in fiber and low in sugars and starches are also good, including non-starchy vegetables and low sugar fruits.
ALL BEVERAGES SHOULD BE NON-CALORIC!!! This is a really important point. Water, unsweetened tea, and black coffee are excellent. Artificial sweeteners are ok, and anything with close to zero calories is fine, such as diet soda and other diet drinks. The only exception to the non-caloric beverage rule would be a protein shake—but even then, the calories should come almost completely from protein (rather than carbs and/or fats).

Another rule is the avoidance of REFINED CARBS and REFINED FATS.

Things like flour, sugar, and oil contain energy that has been separated from nutrients, so they provide energy far out of proportion to satiety and this leads to huge energy overconsumption.
Because they contain REFINED CARBS and/or REFINED FATS, you really have to avoid the vast majority of packaged foods!! Everything pictured below contains excessive energy separated from satiety and choosing these foods will lead to excess energy consumption.
The secret to a low energy diet is FOOD CHOICE. When you choose a food that has higher satiety per calorie, you will automatically eat less energy! Instead of focusing on calories, you are focusing on choosing foods with a high satiety per calorie, and then eating those intuitively to satiety.
Cooking a low energy diet is simple — just cook a high-quality protein, and then cook some non-starchy vegetables.
You can also eat a low energy diet without cooking anything at all! Foods like cottage cheese and smoked salmon require no cooking at all:
ENERGY DENSITY is a very important concept here. Try to choose foods that have as much PROTEIN, FIBER, and WATER as possible, while at the same time having as few net carbs and fats as possible. This allows you to eat a much higher WEIGHT and VOLUME of food, for the exact same energy intake—and that gives you higher satiety per calorie.

In the example below, you see how someone can eat FOUR POUNDS of food from smoked salmon, eggs, boiled potatoes, and greek yogurt—yet only eat 1,600 calories.

In the same example, note how only 0.6 pounds of potato chips is the same 1,600 calories!!
Try to substitute higher protein and fiber foods for the foods you are currently eating.

For example, if you currently eat a blueberry muffin for breakfast, you would be much better off centering your meal around protein, and eating something like eggs and turkey bacon!
For lunch, replace your sandwich with a salad that has a lot of lean protein on it!
For dinner, replace your pasta and bread with protein and vegetables!