What are the things you tried before?
It will be easier to help if you tell us something about your diet and exercise and age and overall health. All things being equal, meaning no health problems altering your basic make-up, eat less and exercise more. Eat better -- lots of veggies, whole grains, legumes, fish, moderate intake of red meat, cut out most of the excess sugar, try not to eat too much of the simple carbs that turn quickly into sugar if not burned, and increase the amount of physical energy you expend. Won't happen quickly, but eventually your metabolism will change and the weight will come off slowly but hopefully permanently. But again, this is assuming you don't have specific physiological conditions that change this basic equation.
In my case, besides the old classic which is to take in less and burn off more, the thing I need to do is delete the soda and other sweet drinks such as juice. Sometimes the obvious is staring us in the face but not registering because it seems like it's too easy.