First and foremost thing is stick by your timetable of whatever u eat... may be u eat more or more fatty... but a timetable or routine is must .... Irregular habit of eating anything anytime is the main cause of getting overweight and many other digestive problems...
Then u must:
1. Replace your afternoon lunch with the fruits like apple, grapes etc (Avoid Juices)
2. Drink as much as water in the day.
3. Less fatty foods... (if u cant avoid)
4. Walk or cycle as much as possible.
5. Add more yogurt or buttermilk in ur day diet...
Obviously there are more to say but start with these few things and u'll see the difference in a few days ....