Plan, record, dilute, pace, eat, leave, and remember (see below). The other part of the answer is to avoid a few of the functions where you know everyone will be drinking more than usual, or occasionally make yourself the designated driver.
Most importantly you need a plan, otherwise you will plan to do what's expected. Plan to pace yourself and pick drinks that are low in alcohol but high in total fluid. This allows you to drink along with everyone else, still experience the often relaxing feeling alcohol is noted for, all the while dramatically reducing your alcohol consumption and waking up fresh the next day. And on that note, keep in mind the next day.
I like to plan an early event the day after a party. It may be as simple as getting up for an early walk or workout with a friend (so I have to be there) or actually attending a function where I need to be fresh and not hung-over. This also gives you a great excuse (if you need one) why you're not overindulging - "you have to be somewhere and fresh in the morning". Tips for reducing alcohol consumption at each event:
• Plan: set your goal by writing down how many drinks you will have, their contents (see dilute), when you will stop alcoholic drinks and when you plan to leave the function. Ex: 2-3 distilled alcohol drinks or 2-4 glasses wine or 3-5 12oz beers would be a sensible maximum (lower range for females or short function) spread over a 4-8 hour period
• Record: write down your drinks as you pour (phone, PDA, note pad)
• Dilute: have your alcohol with large amounts of fluids such as wine/champagne spritzers, distilled alcohol mixed in large glasses of sodas/juices (preferably diet) like a vodka grapefruit, rum or bourbon and diet coke, etc.
• Pace: your spirits by drinking non-alcoholic drinks (beer, diet soda with lemon, lime and regular soda, etc.) in between your alcoholic ones as these drinks look the same. Also If you start with hard alcohol, finish with a wine spritzer but stay within your set limit
• Eat: before and during the events because it often reduces the urge for alcohol
• Leave: according to your plan and remembering you want to be fresh in the morning
• Remember: write down the downside of too much alcohol: leads to weight gain, less than productive often painful following day, which also contributes to increasing weight; can lead to foolishness you may regret and be dangerous to others. Don't regret, rather, enjoy the holidays.