18 yrs old, wanting to loose about 18 pounds

hi,
im 18 years old, have been on this site for about 6 days now, first time calorie counting. i want to loose the fat around my thighs, upper arms, and i need to flatten my stomach. I want to keep the weight off and not have to go back to the process of loosing and gaining again. i want this to be a lifestyle change for the better. anyone in the same boat....