Help on getting a healthier body? ?

Okay, so I do NOT think I'm fat. I just know that like most teenagers in general I have a little fat. I have some fat on my upper thighs and butt and a small amount on my tummy. I do sit ups ans squats so the muscles underneath are fairly tone. Plus I'm usually in sports during school time. I want to get rid of that fat but I can't go on any crazy diets. I still need suffices healthy food because my job is outdoors and includes a lot of physical activity. (Already passed out once due to dehydration and insufficient breakfast) I am going to get a gym pass and I just want to know what other exercises and what diet I should maintain to get a lower fat content without being a crazy muscle head or an anorexic slender type body. I just want my muscles to be able to show my healthy body better. Any advice?