It's not as easy as "losing weight" I was over-weight in high school, but lost around 100-110 Ibs... I was about 230 then... Now currently I'm like... 125-130 Ibs... What helped me was exercising with friends, eating right, and playing "Just Dance..." TIP: When at the gym always bring a friend, working out with a buddy always makes it more fun... ^^ Good luck
Don't eat nutritionless foods that just have calories and nothing really useful for your body. Eat things that have value for your body, like things with protein, healthy fats, and healthy carbohydrates. Healthy fats are found in fish, eggs, & oils, and healthy carbs are in grains and fruit. Unhealthy fats are trans fat and saturated fat, and unhealthy carbs are mainly found in high fructose corn syrup.
Multiply your weight times 12 and that number is the amount of calories your consuming in a day, if you start making healthier choices and the calories you've eaten add up to be less then your gonna loose weight, if it adds to around the same number your gonna stay the same and if it adds to be more then your gaining weight