As you eat, wine is commonly served as well. You may be offered red wine, white wine, or both with differing courses. No matter what you're served, don't raise your glass until your host does so and don't take your first sip until your host does.
Generally, a restaurant with a server will include a service charge with your bill and no additional tip is needed or expected.
Drinks
Luxembourg offers nearly every non-alcoholic drink on the market from milk, juice, and soft drinks to coffee and tea. However, none hold a special place in the hearts of the people because that is reserved for their alcoholic beverages.
There is a divide among the people between beer and wine; Luxembourg produces both in great quality. There are a few local breweries and for many, there is a passion in this drink that is commonly found in neighboring Belgium. However, the country also produces great wines, particularly Rieslings along the Moselle River, which borders Germany and is known for producing some of the world's best Rieslings. Foreign wines, beers, and hard liquors are also easily accessible.
Generally speaking, the tap water is safe to drink in Luxembourg, but check with locals for any particular regional differences. Also, many people may have troubles adjusting to the local tap water, as it will most certainly be different from what your system is used to.