You don't need to compromise your social life to maintain a healthy lifestyle. There is also no need to make a night out a "guess I will be bad" kinda night. I have put together a list of tactics that help me maintain a healthy balance no matter where I am or who I am with. It's all about having the right frame of mind and planning accordingly. These tips don't all need to be applied to survive a night on the town. Just do what you can depending on the circumstances.
Remember why you are out. It's not just about eating and drinking, it's about socializing and connecting with others. I try and put more energy into keeping a conversation going and either catching up with those I know or getting to know new faces than devouring my meal. By shifting the focus away from the food, I'm able to pace myself with little effort.
Make decisions prior to your arrival. Do you want the bulk of your calories to come from your beverage choices or from food selections? Are your sights set on dessert? Asking yourself such questions will help you make smarter choices. If for example, I'm headed to a birthday party, I know that I will want to have some cake so I will steer clear of the mixed drinks (so I don't go overboard on my calorie and sugar intake). Instead I'd order vodka with club soda and extra lime or a glass of wine. Or if I'd rather enjoy a caipirinha (my favorite cocktail made with cachaca, sugar, & lime) then I would pass on the cake and order a fruit plate instead.
Don't forget the H2O. You want to stay hydrated and have your cocktail last longer than 5 min. I like to order some bubbly water, like Pellegrino, and alternate my sips from the alcohol to the water. Some recommend that you have an alcoholic drink and next you should have a glass of water before moving to your next alcoholic drink. Personally, this doesn't work for me because I like to enjoy my cocktail throughout the night and would much rather have my water and alcohol at the same time.
Don't skip meals. It's much easier to make wise decisions if you eat sensibly throughout the day. Otherwise you risk overeating. I've found that not only do I usually overeat if I don't eat normally throughout the day but that I will usually leave with a bellyache from indulging in way too much fried and fatty food.
Know yourself. If you're a volume eater then fill your plate with fruits and vegetables so that you don't go overboard on the mac and cheese. I'm the person who can easily eat a large amount of food that I really like, so if I want to order the cheesecake and know that I am capable of licking the plate clean then I will get someone to share the order with me.
Do your homework. Sometimes it helps to have a game plan. Most restaurants offer their menus online and taking a look ahead of time can help you figure out the type of food offered and what to order. One source that is very helpful is the Healthy Dining Finder.