I lost almost 25kg in about 8 months a few years ago, and didn't find it that hard. Wanna know my secret? Read on.
I did a bunch of research and came up with some simple principles to follow:
1) Fill up on vegetables. Eat a variety. Consume as much vegetable matter as you want.
2) Drink lots of water (at least 2 litres per day).
3) Avoid sugary and/or fatty food (see point 1), and minimise bread.
4) Walk an hour a day, and do some form of strength exercises (I did some bodyweight exercises, such as situps, chinups, pushups, etc).
5) Avoid alcohol.
Watch the fat fall off.
I also started to guesstimate kilojoules, and found this to be useful, but it's not really necessary.
I spent $0 on nutritionists, dieticians, doctors, gyms, equipment and special foods.