Cuisine is one element of Belgian life that reflects its Counter Reformation history. In all matters food related, Belgium is closely aligned with (catholic) France and distances itself from the (protestant) Netherlands and Germany. Belgian cuisine is a variant of French Cuisine. It is largely based on potatoes, cream, butter, cattle and seafood. Being fairly far north, traditional Belgian cuisine is limited when it comes to fruit and vegetables, especially in winter.
One key difference with the French is the distribution of meals. Like the French the Belgians start the day with fresh pastries and bread. Bakeries open before dawn and it is a customary to go buy fresh bread or simple pastries (boterkoeken) for breakfast every day. Belgians may add a boiled egg and some cheese spread but they rarely eat meat, fish, or cereal for breakfast. Preserves or chocolate paste (choco) are the rule. Volume-wise, breakfasts are bigger than in France, where natives rarely eat more than a single croissant.
Neither pancakes nor waffles are eaten for breakfast in Belgium. These make excellent mid-afternoon snacks with coffee but are not breakfast items. Mid-afternoon is also the time for fancy pastries. American style pancakes are absent and all Belgian pancakes are thin crepes, often filled with fruit.
The main meal in Belgium is lunch and nearly everyone eats a hot lunch every day. Shops are closed over lunch time so shopkeepers can eat a good meal. The staple is potatoes and the favorite way to prepare potatoes is fries. All Belgian homes have a deep frier and Belgians will buy a deep frier before they get a refrigerator. Most Belgians think "French fries" is a misnomer and the dish should be called Belgian fries instead. Fries are also the favorite snack food and hamburgers and hot dogs are a recent introduction. Fries with mayonnaise or one of the dozens of mayonnaise-related sauces is the prototypical Belgian snack. Ketchup is rare. Small meat items such as sausages may be added.
Rice is far less popular and finding good rice in Belgium is a challenge. Corn is almost completely absent. Belgians think of corn (maize) as chicken feed.
Belgians will tell you that the prototypical Belgian dish is steak and fries with lettuce and tomato. Unlike the French and unlike what Americans think, Belgians rarely eat horse meat and the habit is restricted to a few regions close to the French border. Belgians also rarely eat lamb.
Beer is the universal drink and until recently no adult would be caught dead drinking a soda. Every restaurant, including McDonalds, Burger King and other transplants serves beer. As recently as 50 years ago, every village had its own (or several of its own) brewery and people would drink the local blond ale. Most native Belgian beers are ales. (Local) Pilsners are now the most commonly drunk beer but this style is an import from Germany. Drinking age in Belgium is 16, although bars will allow anyone to drink beer if the parents agree.
Dinner is a simple affair and consists of bread with cheese and prepared meats (charcuterie). As a rule, restaurants are for special occasions and when going to restaurants people change their eating habits to a light lunch to make room for an elaborate dinner. Good restaurants do not have "seatings" and you are expected to take until midnight (or close to it) eating dinner. Dinners start at 7 or 8PM and mid-afternoon dinners are unheard of. Going to a restaurant is a way to spend lots of money and good restaurants are not cheap.
Casual dining has become more popular, but always expect to pay a hefty premium when eating out. Unless you want to spend outrageous amounts of money for bad to mediocre food, avoid tourist traps such as the market place in Bruges. Just around the corner you can find better fare at a more reasonable price.
It is customary to go to restaurants for special occasions such as Christmas or New Year's eve. At that time, people will eat game (pheasant, hare, wild rabbit, boar, venison, etc.). Seafood is also very popular and two very popular (summer) dishes are mussels and grey shrimp. Belgium also has great oysters and Scottish smoked salmon, but lobster and crab are very expensive and better savored elsewhere.
Belgians drink a lot of wine and every self-respecting Belgian has a wine cellar in their house. Belgium is the top per-capita importer of French wine.
Although there are ethnic restaurants, I would recommend staying away from most. The cuisine is always heavily modified to suit local tastes and rarely resembles the original dishes. Chinese restaurants in Belgium invariably serve Indonesian and Philippine dishes, while Mexican food ( a recent trend) is so unlike what you would expect to get in Mexico that it is not worth the money.
Belgium is known for its beers, although most are novel creations that plagiarize existing beers and were adjusted to suit foreign palates. It is difficult to find good authentic beer but certainly worth the trouble when you do. Another local favorite is chocolates, but the best chocolate is found away from tourist spots in local bakeries. Easter is the traditional time to eat chocolate and all bakeries will make easter eggs.
Another recent introduction that has many people ranting and raving is speculoos paste. Speculoos is a traditional cinnamon and ginger cookie that used to be eaten only around St. Nicolas day (early December) but is now available year round. A few years ago, a paste was introduced to compete with peanut butter -a Dutch import. This paste has become an all time favorite of cyclists visiting Belgium, but it is as new to the country as it is to them.
Waffles too are a tourist invention. While some places in Brussels and Liege (and along the coast in summer) used to serve hand-held sugar dusted waffles as an afternoon snack, eating waffles as a snack for adults was at best a regional curiosity. Belgian families would make waffles in winter time as an afternoon snack for the kids but adults eating waffles was rare. Typical Belgian waffles are fluffy and yeasty with light powder sugar dusting and very unlike the heavy duty sugary contraptions topped with ice cream and chocolate sauce that are now ubiquitous in tourist locales.