By eating less fats and exercising.
How can I make sure I don't get tummy fat?
Drink lot of water and exercise a lot daily. Even a little walk is help.
If you don't want to put on tummy fat, the simple solution would be to:
-eat less/be more mindful of what and how much you're eating
-exercise more
To give you a more detailed answer though..do this:
Take your weight, multiply it by 15. This will give you the calories you need to take in to MAINTAIN your current weight.
So if you are 150 pounds, that would be 150x15 = 2,250 calories/day.
Maintain a diet around here and you won't gain any weight.
If you want to eat more each day, simply add some cardio ...1 hour of intense cardio will burn around 400-600 calories.
Another way for you to more easily maintain your current weight is to make healthier food choices, eat foods which are not so calorie dense yet at the same time satiating...
Namely: Fruits/Veggies/Lean meats
More info on setting this up right here.