Sugar, obviously, in all its forms. Cereal, beans, root veg (except celeriac, strangely). You have to limit fruit at the start too. Funnily enough, you can get away with some alcohol, as long as it is "dry" (that's Baileys out). But you can scoff most veg, salads, cheese, mayonnaise, cream, and the key to the diet is to up the protein - lots and lots of eggs, chicken, fish, meat, yogurt, because it fills you up.
I cook for the family and then just adapt my plateful - i.e. I have my bolognaise with sauted courgette, and I skip rice for an extra pile of broccoli.
There are loads of threads on this, and diet books, I'm not very scientific in my approach but did what worked for me. I lost 1.5 stone over a few months, and it has stayed off for the past year with no trouble at all.