These days a lot of people are overweight. One of the reasons for this is the fact that so many people are dining out so often. Restaurant meals tend to have a lot larger servings than those you eat at home, and they tend to be a lot more calories dense. This means people tend to eat too much, which is not good for their waistlines. However, if you make this a special treat there is no reason why you can't stay healthy and still eat out from time to time.
One thing to do is choose restaurants that tend to serve healthier food when you are dining out. Restaurants that serve food that isn't fried, as well as plenty of soup and salad options, tend to be better than those that focus on fast food or very rich food. You want to have a number of healthy choices available to you so that you aren't so tempted to choose an unhealthy meal. Many restaurants now have their menus posted on the internet (sometimes even with calorie counts) so you can choose a healthy option ahead of time. This is a good strategy.
Another way to eat more healthily when dining out is to automatically pack up half of your meal to take it away so that you don't overeat. You can also choose to order an appetizer as your main dish as these portions are typically smaller. Minimizing the total amount of food you are eating is the goal. This means you might want to avoid the bread basket that some restaurants put on the table.
Eating a broth based soup or a salad (with minimal dressing) at the start of the meal can help to fill you up so you are less tempted to pig out on large amounts of appetizers or main dishes. Another good strategy is to put your silverware down in between bites so that you can eat more slowly.
There is nothing wrong with indulging yourself and having a small treat when you are dining out. However, you don't want to ruin your diet by eating everything indulgent at once. Maybe one time you can share a dessert with a friend, and another time you can have an alcoholic beverage or split an appetizer that is a bit high calorie with a friend. If you eat the bread, you don't want to have a drink and dessert as well.