There is one holiday eating tip that you need to do every day. Eat protein with every meal.
At your holiday parties, get full on protein foods first. It will help you eat less of the condiments, desserts and other high-fat foods at the party. Most holiday parties have plenty of foods loaded with protein. Nuts, ham, turkey, chicken, fish, etc. are great foods to eat. Protein helps control your blood sugar if you happen to eat carbohydrates.
It takes your body longer to digest protein, so you will fill fuller for a longer period of time by eating more foods rich in protein (this should help you eat fewer calories during the day).
Protein is also used by your body to repair and rebuild damaged tissues as a result of a tough workout (especially weight training). Quickly digesting protein shakes work well after a workout. Other daytime and nighttime meals could be comprised of slowly digesting protein (such as lean meats) that will give a constant release of amino acids into your system during the day and overnight.
So, when used right, protein will help you build a lean body and help your weight loss/fat loss efforts.