It is best to eat lots of fruits and non-starchy green veggies, go slow on fats, eat carbohydrates in moderation and increase your
protein intake (lean cuts, whites of eggs etc). Drink plenty of water and non
fattening fluids such as clear soups etc. Look for hidden calories in salads and soups and avoid them (eg: cheese, butter, dressings etc).
Also, you need to exercise regularly. You need to start slow and then build up stamina as the days progress.