Eat a light breakfast and lunch, but don't forget to save some calories for the evening. Drink some water before leaving the party. Concentrate on foods that are not usually available, and then eat them in moderation. Remember the law of diminishing returns. Beware of the bubbly.
Alcohol contains almost as many calories as fat does.
Combine it with creamy or sweet mixers, and you get even more calories. Alcohol also lowers your inhibitions, which might make you careless about your food choices. Alternate between water and alcoholic bevarages, or simply forget the bubbly and drink soda water, water or other non-alcoholic bevarages. Keep things in perspective. If you lose control at a party or gathering, don't try to make up for it the next day by starving yourself.