Here are a few tips to add from our trip the first week of August 2014.
We enjoyed Norway in general, but without planning, we would have enjoyed it way less. The cost of most everything was outrageous compared even to being in the UK, where we were the first week of our trip. Feeling that most everything is too expensive to enjoy felt oppressive after a week. I am not a cruise enthusiast, but I can see why people visit Norway on a cruise boat or just do the Nutshell in a day from Oslo. If you are from the Pacific Northwest, it will feel very similar to home. If I was doing this again I would do the Norway in a Nutshell, then visit Sweden as, amazing as it sounds, the cost is much more reasonable,
Norway is incredibly expensive for everything - if you are using the USD. Be prepared not to eat out - even an ice cream cone is $5 USD, hamburger with no fries about $20. Get breakfast at your hotel - it is likely the nicest affordable meal you will get while on vacation in Norway,
Oslo hotels do not have air conditioning, and almost no ventilation. Hotel windows may not open more than a few inches. If it is nice outside you will likely be frying inside of museums and your hotel, so be prepared.
Bring an umbrella for frequent but passing rain storms. We had to buy one and it cost $28 but was worth every penny to enjoy the folk museum which is mostly outside.
Bring food with you like granola bars, etc, to keep you going. We brought almond butter, Starbucks Via coffee packets, crackers, trail mix and granola bars. We also brought a small insulated flask that we filled with hot water. Renting a car for travel outside of Oslo was a good value with two of us.
The Oslo Pass worked really well for us, although some of the museums on it are not very interesting or are free anyway. If you stay downtown you will be walking distance from most everything. During our visit the trams and trains were having trouble due to the heat so the pass may or may not help with the transportation cost.
If you are planning to stay anywhere besides a hotel, and particularly outside of Oslo, bring twin sheets to save money. This saved us about $30 per night. Also note, doing laundry is expensive. In a camp ground $18 to wash and dry one load ourselves.
Be aware that anywhere that if you are not a tourist area, everything except mini-marts, will be closed on Sunday - everything! We ended up buying bread and jam to go with our peanutbutter at a mini-mart because everything, except one or two cafes, was closed. We were driving from Oslo to Lom, and when we arrived in Lom discovered that the grocery store was open, but again, everything else closed.