Do you want to lose weight or need to lose weight? Height, current weight, target weight?
Be in a calorie deficit through diet and/or exercise.
A sensible rate of weight loss is up to 1kg/2lb a week.
Eat a balanced diet, with the occasional treat, and stay hydrated. Make your own meals so you know exactly what's in them, especially sauces; even savoury items and those labelled 'diet', 'light' etc can be high in sugar.