1. Choose a cheat day. Choose one day to eat and drink everything you want... but just one! The rest of the week stick to a strict diet. Cheat days are a good way to reward yourself, avoid feeling "left out" of the fun, and even jump-start your metabolism.
2. Go all out on meats and veggies. Eat as much meat, veggies, and sugar-free veggie dip as you want. You'll fill up and feel good. You also won't have a spike in blood sugar and insulin production, meaning you probably won't put on much fat. Avoid just about everything else, especially baked good and anything else containing refined sugars and flours.
3. Stick to wine spritzers. While everyone else is drinking "liquid candy" in the form of high-sugar holiday cocktails (e.g. eggnog) and putting on pounds by the minute, you stick to wine with soda water/seltzer. It makes a refreshing low-calorie/low-sugar spritzer that will still help to put you in the holiday mood!