Your age is not going to have much to do with your diet...
What is more likely to have an affect on what diet you go on are what your preferences are.
There are so many different diets out there.
However, the best thing to do is to first find out your maintenance calories:
Your body requires a certain amount of calories to maintain it's current
weight (body weight in lbs x 15)...so if you were 150 pounds, that would be
150x15 = 2,250 calories/day.
To lose 1 pound you need to be in a deficit of 3,500 calories. So if
you ate 500 calories less than this 2,250 each day (1,750 cals/day) you would
lose 1 pound each week.
Couple that with 1 hour of cardio each day (500 calories burned/h on
average)..you'll burn another 1 pound a week.
As far as what you should be eating, it's a good idea to fill yourself up on low calorie foods such as veggies, lean meats and fruits.
Aside from that, here are a few other things to add to your diet:
-nuts, oatmeal, brown rice, yogurt, no fat cottage cheese
Really, whatever helps you adhere to your diet, you should include, but minimize processed foods.
You can go out and drink with your friends or eat junk food once a week, just make sure you keep track of what you're putting in your body, don't undo a whole week's worth of work.