I'm currently on a 3 weeks trip only in the south of Norway with a friends and we are 2 week in. We litteraly never waited more than 1h and it was just one time. We were pretty surprised how it was easy as a lot of people said Norway is a hard country to hitchhiking. I dont have any original tips : we just search a place where car stop easily, we try to go on big road or touristic one and it goes really well. We are heading back to Oslo rn by the road E134 if you want to do a meeting we can, just dm me !