When eating out you still want to be mindful of your dietary goals, and avoid any pitfalls. There are a few things you can do to ensure you stick to your dietary goals:
Pick one starch. Many restaurants present you with bread while you're looking over the menu and waiting for your food, but if you're about to order a starch-heavy dish,then you shouldn't chow down on bread while you wait.
Watch your veggies. How a vegetable is cooked will heavily affect its health rating. If a vegetable is swimming in butter, then it isn't exactly healthy. Likewise, foods that are steamed and grilled will be more healthful than sautéed or fried.
Make limiting your portions easier. If you're ordering a large meal and don't want to overdo it, ask for a to-go box or have half of your meal packed up in advance. That way you won't keep eating out of habit or because the food tastes good.
Treat yourself. If you have an unhealthy favorite, allow that to have a place in your diet (in moderation of course). When you don't feel deprived by your diet, it will be much easier to stick to it and avoid binging.
Eat light. Order appetizer-sized entrees if you're looking to have a small meal, or split several appetizers between friends to increase variety without increasing the amount of food.