I lost a total of almost 70 pounds during the course of two years, from 200 pounds (yikes) to my current 135. It was maybe 95% diet for me and 5% exercise. I hardly exercised and still lost the weight. The biggest tip is just the simple rule of calories in vs calories out.
I used an iOS app "Myfitnesspal" to track calories. I ate whatever I wanted, even fast food, on an almost daily basis, but wouldn't go over 1800 calories a day. 1800 cals was my limit for my weight and height in order to lose weight. It's different for everyone.
I was also very strict on the calorie tracking. I tracked everything from the oil I cooked with, every liquid I drank, sauces and dips I used, and even the black pepper I sprinkled on food and soy sauce I used for sushi, etc. A teaspoon of black pepper is five calories, a tablespoon of soy sauce is 25 calories. Might seem insignificant but that's how strict I was with the calorie tracking and is probably why I lost all the weight. People often forget to track these things and the calories add up!
So I didn't exercise.. I didn't really eat any healthier.. but I still lost 70 pounds lol. The "calorie in/calorie out" rule, people. Losing weight was simply a mathematical game for me.