Opinions on tipping in Denmark vary. According to Danish law, any service charge, including tips for waiters, has to be included in the price in restaurants. However, waiters obvious appreciate a tip, and according to some sources, it is customary to leave up to 10% to the waiter, if you are satisfied with the service. Others say that it isn't the custom to tip in Denmark at all, as wages, even for service staff, are sufficiently high. In one way this is good, as tips aren't expected, but in another way it is a shame as service staff don't expect tips and so don't go out of their way to provide good service in order to secure a tip! Ultimately, it is up to you whether you want to tip or not, especially in the case of exceptional service.
In Denmark it is very important not to skip in front of a person, when you wait in a line. It is considered very rude to do so.
Correction: Don't get too hung up on the above advice as a testament to exactly how bad Danes are at forming lines many shops have a number system to ensure people don't jump the line.Danes in general are a very quiet and patient people. They are seldom loud and self-indulgent (except for the occasional teenager). They keep to themselves out of courtesy and consideration for others. Don´t take their reserved nature as indifference or unkindness, because it is often more due to friendliness and their respect for your privacy. Just like, if you meet a horse or a dog for the first time - you don´t run up to it screaming your head off - it will be frightened if you do so. No, you sit quietly with a friendly attitude, until the creature comes to you. Then you can stroke it. Much like that, they sit quietly and wait to see if you are interested in contact. If you show interest, you will see, that they can be as talkative and social as every other people around the world.
Much like that, it is considered rude to be loud and noisy, blabbering about all your achievements. Showing off, making a scene, drawing attention to yourself is not good. Instead you should respect others privacy or ask them "How are YOU doing?". This has a downside though, because they can sometimes become so humble and focused on not drawing attention to ourselves, that they suppress ourselves to the point of stupidity. The trick is to find a good balance.
There is a word in Danish that does not exist in other countries. "Hygge". It means a quiet happy cosy atmosphere of people having a good time. They strive to have this atmosphere everywhere they go - at work, at home, with friends and relatives. If they haven´t had it "hyggeligt", they often see it as wasted time, and try to achieve it next time. Sometimes, fx when they get drunk, it can be a little louder with singing and laughing, but the goal is still "hygge". Even the days little chores can be made "hyggeligt". Fx if you have to do the laundry, you could choose to sit and be bored and count the minutes till the washing machine is done. But you could also find a comfy chair, a good book and some music while you do it. When the day is done, you could turn on the telly and sit and count the minutes till you go to bed, thinking about all the things you should have done today and didn´t. But you could also light some candles, have a glass of red wine and have a chat with your spouse about a funny thing, that happened at work today. You haven´t experienced Denmark, till you have experienced "hygge".