As the poster above said, it's not particularly difficult to get married in Norway, per se, but there is quite a bit of paperwork involved. One thing that should be made clear is the difference between getting married in Norway and applying to stay for family immigration. Getting married isn't too difficult, but family immigration (ie: fiance permits, family visas, etc...) adds a bit more work and a lot of time/patience to the process.
In terms of getting married, you need to make sure you're allowed to get married in a foreign country. Some countries won't recognize a marriage if it happens outside their borders.
My first recommendation is to look at the embassy of your home country even if you're not applying from outside Norway, sometimes there are specific things you need regarding the marriage itself as well as family immigration. For example, as a Canuck, I needed a "non impediment to marriage" document, but since Canada doesn't provide those, I needed to get several other documents instead from several different agencies. I found all this information on my embassy's website.
You should also look at the local municipality and find out what they will need in order to allow you to legally enter into marriage. For example, to get married you also need to prove that you're in the country legally. You cannot get married on a tourist visa (however, if you do not need a tourist visa to enter into the country (for a duration of 90 days), then you can get married so long as it happens in the 90 days).
Your next favourite site should be UDI - the immigration website. They are not always the easiest to read, and the website is sometimes out of date (for example, they still have registered partnership as an option, but that was eliminated a few years ago and replaced with marriage). But the UDI website does have all the documents you need and checklists to make sure you get everything.
Whatever you do, make sure you apply for the right thing. UDI has denied applications on the basis of applying for the wrong visa, not submitting enough documentation, etc... When I say apply for the right thing, I mean make sure it's the right application. A lot of people have been rejected because what they wanted was a fiance permit, but they ended up applying for a spouse/family immigration permit instead.
The fiance permit entitles you to enter Norway with the intention of getting married in Norway. It's valid for 6 months and requires you to get married in that time. After you've gotten married, you then (assuming you want to stay in Norway) apply for family immigration for spouse (this is assuming one of you is legally allowed to stay in Norway: ie: permanent resident, citizen, etc...).
You cannot apply for the fiance permit from Norway unless you are already there on another visa, I believe. However, you can stay in Norway while awaiting the family immigration decision by UDI and during any appeal process.
This is the UDI page for family immigration. Unfortunately I can't really help with any more information on the marriage part itself because that's dictated by your specific situation and your home country.
http://www.udi.no/Norwegian-Directorate … migration/
Hope that helps.