One of the biggest reasons I failed to lose body fat previously was by making things too complicated.
I think this is another of the difficulties in dieting - one tends to look at what the already lean / slim people are currently doing, rather than what they used to do.
As bodyfat goes down / muscle mass goes up, the complexity of the exercise / diet increases by necessity.
But for a beginner or overweight person, almost anything they do is going to be better than what they are currently doing (assuming they are just getting started).
With this in mind, I think the most important thing to start with is this:
Change your way of thinking such that high calorie foods that may have been a staple in your diet (potatoes, pasta, bread, rice as well as the usual suspects like chocolate, sweets and cakes) become treats. The vast majority of the diet should be vegetables (the colourful, generally above-ground variety) and berries. Meat is a contentious issue that we'll get into later, but for now, keep it lean if you eat it (chicken breast, fish, turkey, lean beef etc.) As a vegetarian myself, I have no problems meeting my protein requirements using readily available alternatives such as Quorn, soya (both milk and "meat-free" products), cheese, eggs, whey protein, cottage cheese etc. If you're a vegan, please post some comments on how you meet your protein needs (remembering from previous posts that we want to hit ~1g per pound of body weight).
In practical terms, this means changing a typical meal such that the amount of potatoes are gradually reduced and the amount of meat and vegetables increased. Doing this over the course of a few weeks will be easy and you may find that it leads to automatic weight loss.