In Norway, tipping is not required anywhere. Service (as well as sales tax) is always included in the bill at restaurants and bars. However, it is usual for Norwegians to leave a tip in restaurants and bars if they are happy about the service. You can round to the nearest 10 or 100 NOK (leaving coins), a 10-15% tip is considered generous. For Norwegians it's uncommon to tip taxi-drivers or cleaning staff at hotels. Other service personnel almost never receive tips.  You may sometimes encounter in some restaurants the servers demanding a tip of at least 10%.  This is not required although they may act as though it's compulsary.  In real restaurants (where customers are served at the table by a designated waiter)  tipping is very common.

Bargaining or haggling prices will in most cases get you nothing but puzzled looks and/or angry vendors. The price is on the tag, and unless the item you want is damaged or highly overpriced (higher than usual in Norway) haggling will usually not get you anywhere. Bargaining or haggling is mostly restricted to second hand sales and car dealers.

Be careful in discussing politics and religion with strangers or accidental acquaintances. Many things in Norway are expensive for overseas visitors. This is largely due to 25% government  sales tax on just about everything. Criticizing prices is of course legitimate, but can easily be felt as unfair and uninformed. The same is true for hunting and eating whale: Some  Norwegians eat whale meat and find that perfectly natural.

Norwegians are in general informal and there is in general no, or very little, difference between "high" and "low" in society.  Except, perhaps, for the King, all are adressed by "du" (Norwegian second person singular "you"). "Hei" is informal Hello, while "god dag" is more formal "hello".  

Norwegians are not known to be open to strangers.  In fact, they have a reputation for being shy or reserved, this can be perceived as aloofness, and it is apparent in every day life.  Service employees just do their jobs without wanting any sort of interaction with the customer at all.   There are exceptions to this, of course, but they are rare. In bars and clubs however Norwegians are happy to talk to strangers. Moreover visitors should not hesitate to approach Norwegians to ask for help and advice, as Norwegians are generally happy to help out.

The norwegian word for "please" is "vær så snill". However they choose to forget this a lot nowadays. Being calm and keeping voice down is considered a virtue in Norway. Loud voices are regarded as rude or ridicolous, aggressive or silly, or Norwegians will simply assume you are drunk. Shouting or whistling for a taxi is considered rude in Norway, and drivers are likely to ignore you if you do. Wave your hand at, phone or simply walk up to one with a lighted sign on the roof.

When on buses and public transport it is unusual to say "excuse me"  to a person blocking your exit or seat. The codex here is to grunt , shuffle , clear your throat  in fact anything that gets attention . If no reaction is forthcoming you wil just be shoved or pushed over.

While "tipping" can mean giving a gratuity in english, it means "betting" in Norwegian. If you use the word "tipping" the Norwegians will think you are refering to placing tips on a gambling website. "Tips" or "driks" are used in Norwegian to refer to gratuity.

For men it is customary to take off your hat, or cap, when entering a house, and in particular when seated to eat.

Always take off your shoes when you enter a private home, unless the host offers that you keep them on. In winter this is compulsary as snow, salt and dirt will ruin the floors. In Svalbard, in the very extreme far North, you can not forget this rule as racks of dirty outdoor shoes are placed at the entrance. 

In Norway many public and private sidewalks are NOT shoveled, there is only more coarse sand added.  Trying to pull a heavy suitcase that has small wheels over such sidewalks is almost impossible.  Since most Norwegians carry various sizes of backpacks, this is no problem for them and they seem quite oblivious to the needs of foreign travelers.

Nearly all Norwegian sidewalks have "rain gutters" cut into them that are supposed to channel the rain from the downspouts of buildings into the nearby gutter.  The actual result is an endless series of  opportunities to twist your ankle if you don't watch it!  And, if you are pulling a heavy suitcase with small wheels, it is guaranteed that it will be wrenched out of your hands several times as the wheels catch in the channels.  Suitcases with larger wheels work much better.