Here's some travler tips.
1. Take up a big loan, you'll need it as few citys in the world are more expencive, a .4l beer will cost you up to $15 USD
2. Go during July/August, best weather, lovley and green everywere, DON*T go in winter time unless you love cross country skiing.
3. Take the train up west to the Frognerseteren(end station) And you have a big great forest to walk in, just 30min with train for the city center, you can just pick a direction in random and walk for days, this is also the place to go if you want to do cross country skiing during the winter.
4. Take in the museums, like the ones at Bygdøy, here you have a viking museum, a museum with the whole ship fram, and kontiki, you also have the outdoor museum names folkemuseet(peoples museum) with buildings from norways history from viking age up to the ealy 20th century.
And while you are there you can take a dip in the oslo fjord as there are sevral beaches there, even a nudist beach if you're into that.
5. Take a trip to vigelands parken, acording to some conservative Americans it's a porn museum.
If you are at the right time the 4th of july, the Americans living in the city have their thing there.
6. Take a trip on a boat in the Oslo Fjord some nice sceeics.
7. try a Pizza Grandiosa, the official norwegian frosen pizza
Thats it for now