Ideally eat them raw as it reduces the oxidation of polyunsaturated fats.
You need to do this about 20 minutes BEFORE your meal to give your brain time to recognize the nutrition and reduce your appetite.
This works because the healthy fats (yes, healthy fats), fibre, protein, and micronutrients in nuts help to satisfy a lot of the nutritional needs of your body, thus reducing your body's "eat" signal, since it recognises that it already has a lot of the nutrients it requires.
Doing this will also increase your intake of healthy, nutrient-rich calories, multiple times per day, not only reducing your food cravings and over-eating, but increasing the percentage of your calorie intake from healthy snacks as opposed to other, less healthy options.
This will help in decreasing body fat.
You might also want to try drinking a glass of water (filtered of course - not tap) with the nuts, 15-20 minutes before meals, since the body can sometimes mis-read thirst as hunger. So drinking a glass of water before meals can also help to reduce appetite and prevent you from over-eating, or eating when you're actually just thirsty.
Give it a try - you might be pleasantly surprised! :)