From the author of "The Social Guidebook to Norway"
 Sign up into an organised activity
Sign up into an organisation, a sport group, take part in dugnads, in your kids activities, etc. These activities and groups are what I call "frame activities". Norwegians like to socialize within frames, in an organized manner.
Through these frame activities, you will create social contacts with other people in the group. The communication will probably be pragmatic at first and focused on the activity of the frame. Social bubbles will slowly form around these activities and each activity will have its own social bubble linked to it.
You can safely interact with other group members part of the same social bubble when doing the activity linked to that social bubble. Slowly the social bubble may start meeting outside the framework of the activity it was created around, e.g. you played football for a few months and get invited to have a pizza with the football team. Only the members of the social bubble will attend this new activity and you cannot invite outsiders that did not first contribute to the frame activity of the bubble, e.g. you cannot invite a friend you live with to come and have pizza with the football team.
Social bubbles are rigid in Norway. This is what makes it very challenging to make friends if you do not first get involved into a frame activity.
 Carefully invite someone outside a social bubble
If you find some of the people especially interesting in one of your social bubbles and want to hang out only with them, you need to take careful steps.
You need to find a reason not to invite the others. Since the social bubble was formed around an activity that the whole group was doing together, every member have "owned" their Norwegian right to be invited to any activity fellow members would do together.
If you suddenly invite only some of the bubble members to meet, they may feel uncomfortable with that and ask to invite the other ones. Norwegians are raised by being told to include everyone, even those who they do not have much chemistry with or do not appreciate. When you are a Norwegian kid, your schools, parents and society will create groups for you to be part of and you will be forced to include all members in all activities. Norwegians become very scared of rejecting others and this continues even when they are adults. If you try to invite only part of a group to meet, Norwegians may see this as a rejection towards other group members.
In other words, they will not let outsiders come into the social bubble they created around a frame activity, nor will they let members meet without the other members of the bubble.
 Give a practical reason why to meet
You need to have a very good reason to invite only some members of the social bubble. Giving a "practical" reason works best. If you can orient that practical reason towards an increase of efficiency, that is even better. You are providing a rational, fact-based justification of why you decided to invite only specific group members, e.g. "I am inviting you for dinner because you live close to my place, it is efficient to eat together before driving together to the football practice."
If you manage to meet only with some of the members of a group a couple of times, you will have managed to create a bubble within a bubble.
Then you can relax the justification, e.g. you can organize a dinner a day when there is no football practice, and say “I just got this really cool fondue set I would like to test. The set is only for 6 people."
Continuing to provide a practical justification "I have a fondue set i want to test" (i.e. i am asking your help to test it) and providing a reason why you cannot invite the whole group (i.e. the set is only for 6 people) will make Norwegians feel more comfortable to get out of their social bubble and accept your invitation for an "unframed" activity.
They can justify to themselves why they are doing it: "I am helping him test his fondue set, and so i do not owe anything for the dinner." And feel ok about not inviting the others, because they can justify it for themselves: "There is only place for 6 people."
 Keep it non-committing
At this stage, it is important to refrain from giving an emotional justification on why you invite a Norwegian outside the bubble. Expressing something such as "You are interesting, I want to get to know you better" will make Norwegians feel uncomfortable. This is too much interest and expression of emotions at such an early stage.
Do not make Norwegians feel like they owe you something, nor that you are very interested to get to know them. They will feel trap and feel like they owe you something.
While in many cultures, friendships and relationships develop around giving and receiving with the idea that you give something to someone, that person owes you back and will give back in another form. In that way the friendship goes forward and trust is established.
Norwegians do not like to owe to others. They build friendships by taking part in activities and keep their relationships equal at all time and non-committing. The word in Norwegian is "uforpliktende". Make all your social contact "uforpliktende" for Norwegians and you will be much more successful.
 Keep it equal and in balance
Do not cook a three-course dinner and spend hours preparing it while paying for all the food. While in many cultures, this is a great way to show interest towards others, show that you want to get to know the person, that you are invested in building a friendship - in Norway you will just make Norwegians feel uncomfortable. Cook a simple dinner at first and ask your guests to bring the wine so that cost/effort be equal between the host and the guests. After a couple of years, when you are really good friends then you can make a three-course dinner with nice wine, but do not assume that you will be invited back to a similar dinner.
In Norway, you give to others when a strong relationship is established, not as a way to establishing one. Things should be equal and in equilibrium, especially at first the "pay-back" time is really short. When the friendship is established, then the "pay-back" time can be a little longer.
You shall also make sure that your new Norwegian acquaintances feel like they can escape the newly born friendship at any moment. This is the "uforpliktene" part again.
As we discussed earlier, Norwegians are raised with the idea that they shall not reject others. They thus become very careful in building new relationships, they do not want to "get stuck" with people they actually do not like that much. They know that if they owe something to the other they may not be able to "get ride of" that person afterwards, so they prefer to keep all interactions equal and in equilibrium. Once you established trust, over a few years, Norwegians then open up and are fantastic friends.
Keep your distance, and make Norwegian feel like they can leave at any moment, and you will be more successful in your Norwegian social interactions.
If you want to read more about Norwegian friendships and relationship, have a look at my two books, this blog article is inspired from them.